Published by Maney Publishing (c) IOM Communications Ltd 3 nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International 238 nseltdy h edfrtio eddbak neaie.Scn,temcotutrlfaue and a features also microstructural is the safety Second, examined. Since usage. o and material flexibility, in blanks reduce design blanks welded increased can welded with Tailor tailor weight growing. for reduced need is the aluminium today, implemented steel reviewed. commonly in becoming be most are will blanks common; alloys welded increasingly Tailor aluminium future. automotive near of in the ing in further expand to projected decade. structures next is autobody is the and in savings aluminium a increasing, weight from of deliver is far use to ability is so structure production, The body limited, automotive factor. of steel important In bulk a an the of accelerating. e tute is powertrain reduction are weight improved automobiles to improve in addition to economy attempts agencies, fuel government as well consumers as among grows awareness environmental As Introduction DebRoy T. and White, R. D. Zhao, H. of welding alloys laser aluminium in automotive problems and issues Current oyacietr sas ieyt neg change undergo to likely also is architecture Body eerhr nti il.IMR Dearborn, Co., Motor Ford USA. Laboratory, MI, is Research White Ford Dr and at USA of 16802, PA Department Park, the University State University, in Pennsylvania The are Engineering, and DebRoy Science Materials Professor International. and ASM Zhao and Ltd Mr Communications IoM 1999 © field. this in researchers and engineers, welding the industry, in automotive engineers practising welding, not in are specialists who engineers for materials written and is scientists review The presented. is aluminium alloys grade the automotive in of trends welding future laser on outlook an are and welding identified laser to related questions important unanswered several Finally, discussed. are based remedies science their and grade alloys automotive aluminium welded laser in found defects encountered commonly Third, are evaluated. weldments critically these of properties and the structure Second, examined. alloying are and vaporisation pool, element weld the and in flow transfer fluid heat absorption, energy as these such of alloys welding laser during occurring physical processes important the of understanding the current First, perspectives. different from and interpreted examined critically is automotive alloys series aluminium 2xxx some of and welding 6xxx, laser 5xxx, the on review research this available In the blanks. welded tailor and of aluminium use increased the through of structure weight body the reducing in critical technology a enabling is welding Laser lightweight alloys. especially aluminium materials, new through of vehicles use of the weight the decrease increasingly to is aiming industry meet the to standards, order new In these products. its by of gases emission greenhouse the reduce to fuel and average economy fleet its increase to demands simultaneously facing is industry automotive The ffi iny vehicle ciency, / 345 ff er pn agn rmlsrculn ihauiimto aluminium with coupling laser from ranging open, eet,icuigprst n o rcig on in found encountered cracking, hot commonly and porosity the including Third, defects, evaluated. cally be will surface pool weld vaporisation the and at pool, elements weld alloying flow the of in fluid transfer absorption, heat important energy of and welding including the laser alloys, of during these occurring understanding processes current physical the weld- First, laser the in problems and resulting issues the Current of joints. metallurgy physical and chemistry the remain questions Fundamental technology. consti- mature will which alloys 6xxx and 5xxx the particular ehnclpoete ftewlmn ilb criti- be will weldment the of properties mechanical lnsi lmnu ilas eur e joining new production. require volume high also support will to capability aluminium welded in tailor Introducing blanks RSW. require than will when other hydroforming via processes robust made use less sections increased and closed Further, costly of structures. more aluminium is on used it cost, o assembly low structures, the and body for steel process stamped ideal nearly of construction. a autobody is in RSW While used important now most alloys. the process is aluminium welding (RSW) automotive welding spot for Resistance technologies drops. structure in ing body as the well are of as technologies weight aluminium these the in as of implemented steel, All be seen. decreasing to be likely sti also further and will produce strength sections, ness, structural to enhancing used piece while be weight, single can that spaceframe complex hydroforming or as technologies spaceframes, of such use safety, of Increased expected. and use subassemblies weight increasing vehicle with between o architecture to relationship vehicle needed the be some may concern, changes public growing nraeflxblt na g ficesn ‘mass increasing of age and investment, an single capital in a customisation’. reduce flexibility aluminium, will and increase source steel, mild strength power including high today, than much steel, materials a future of of Since composed variety diodes be future. wider to near likely laser are the structures high state in vehicle laser in prices solid used YAG lower be while promise of to automation, delivery ability its volume optic tech- enhanced fibre laser have energy, as in such developments nology, New tailor structures. produce hydroformed frame in to distortion ability reduced and the blanks, ben- welded flanges, input, potential thinner heat welding’s are low body laser efits speed, Among automotive high flexibility. its advanced and of of because construction structures the to nvtby hswl edt ed o e join- new for needs to lead will this Inevitably, plcto flsrwligt lmnu,adin and aluminium, to welding laser of Application approach interesting particularly a is welding Laser ff e sussurrounding issues set ff rn robustness ering SN0950–6608 ISSN ff - Published by Maney Publishing (c) IOM Communications Ltd on emty h ieadntr ftepam omnybelieved. commonly forma- the to due was absorption plasma in increase the dramatic certain of a the at nature surface, drastically the and increased absorp- several absorption of beam size the However, laser nature the that on the metal. geometry geometry, as joint the joint laser and such formation of the formed. factors laser of resistivity other not wavelength of the the absorption is by and surfaces the plume determined that is metal plasma indicates energy a clean (2) when Equation of vacuum during irradiation accurate in are laser (2) vertical equation using Calculations bopino ae nryb aeil eoe oeo h ae emwt h eddmtrasdrastically materials welded the with beam wavelength laser the characteristic of a with laser Nd–YAG state The more welding. becomes materials during e a by energy energy also laser laser of metal absorption the of concentration in absorption the elements the and alloying pool, volatile weld of the above existing series the using absorptivity for Bramson formula (cm). accurate wavelength the expansion: ( resistivity the temperature is at emissivity nig e otefloigrlto o absorptivity direction for normal relation the following in the their to media, led non-reflecting findings internally for wavelength oteasrtvt ttesm eprtr and temperature same the at Com- absorptivity study. the experimental to Kirchho from with bined metals polished oiaefrua o acltn h msiiyof emissivity the calculating be for metal formulas can Rubens the roximate and absorptivity of resistivity Hagen the electrical substrate. the electrons. surfaces from free metal calculated by clean absorption For conductive multiple on of largely because metal keyhole. the the within of other reflections the absorptivity welding, On the laser e metal. during transfer formed energy the is the keyhole of a absorptivity when mode hand, the conduction to e to During transfer ent energy materials energy. the welding, irradiated output laser the laser by the absorbed energy the nrytase e transfer Energy efficiency transfer Energy ntelsrwligo uooiegaeauiimntdta h nryasrto slwo h as the on low is absorption laser energy pulse the s 2 that J, noted 200 a of absorption aluminium of grade presented. automotive extent be trends of will the future welding alloys on several laser outlook an the Finally, and in identified alloys. weld- be this will these to ing related of questions unanswered structure important the and est ffe lcrn ntesld hc makes which solid, the high in the poor to electrons The part in free low. due of is very energy density is laser the aluminium of coupling by energy beam 10·6 of CO the than 1·06 of absorption Energy light. of reflectors CO best the welding of the in con- one processes analysed, physical be aluminium the will both remedies sidering based and science alloys their aluminium grade automotive welding laser where ffi g g h bopino ae nryb easdepends metals by energy laser of absorption The Experiments in stelsrwvlnt erae.Tesolid The decreases. wavelength laser the as cient l l T) (T T) (T m m g = = m. l rvdsbte opigwt aluminium with coupling better provides m T) (T e e l l T) (T T) (T 2 ae ihacaatrsi wavelength characteristic a with laser and 4,5 = = ffi V + hwta h bopino laser of absorption the that show 0·365(r/ 0·365(r/ ff inyi enda h ai of ratio the as defined is ciency e ffi m ttemperature at cm) 0·006(r/ l slwta h msiiyi equal is emissivity the that law ’s T) (T inycnb uhlre than larger much be can ciency l l r h bopiiyand absorptivity the are ) ) 1/2 1/2 T l ) 3/2 − 1 n wavelength and 2 rtdvlpdapp- developed first 0·0667(r/ ...... 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(1) eeoe more a developed ffi inyi equival- is ciency T, l ) and ff l l hoe al. et Zhao ,r c losso htteeeit hehl ae power laser threshold a exists there that show alloys ect is 3 ino ehl ahrta h ne fmligas melting of the onset that the than showed rather keyhole and a of power tion beam laser found of They alloy. value 5456 cavity. and aluminium the pure by in tion beam laser the Eager and of Huntington reflections tiple bopini eivdt ecnrbtdb h mul- the by contributed be to believed is absorption bopin h iiu oe est eurdfor required density power minimum The absorption. est bv hc ehl sfre n coupling and formed is keyhole a which above density alloys. aluminium of welding 10 laser about is formation keyhole oe est scnieal oe o Nd–YAG materials. for same the lower of considerably welding is laser density power iimadisaly svr low. very is alloys its and minium iin,teasrto flsrba nryb alu- by energy beam laser of absorption the ditions, ihu n ehl omto.Udrsc con- such beam laser Under a formation. by keyhole irradiated was any obtained surface were without results flat above a the All when di alloys. two the the to of attributed was tion n ·–·%b 09aly h di The alloy. 7039 by pulse 6·9–9·0% s and 2 J, 220 a of absorption The alloys. aluminium a on ob nterne1–5 y58 alloy 5083 by 12–15% range the in be to found was h bopino CO a of alloy. absorption the 5456 prep- electron free the surface lower in by same concentration explained the be can with which aluminium aration, pure has of alloy also that 5456 is that coe It 1 absorption Table surface. in an data smooth to the the due from of observed be reflectivity to high appeared the beads specimen glass electropolished by the surface. absorption was the light absorption in to embedded due increased free be the the to decreased in thought sandblasting, whereas the the of surface, to of the case at due absorption concentration was increased electron the specimen It that anodised energy. beam believed laser the was of absorption the decreases, atyices,weeseetooihn somewhat electropolishing whereas signifi- increase, anodising cantly and sandblasting samples, received lcrplse 5 7 22 20 5–12 4 27 22 99·999%Al Electropolished alloy Al received 5456 As Sandblasted laser s Anodised 2 J, 200 preparation Surface from absorption Power 1 Table lmnu lo yclrmty al summarises 1 Table calorimetry. by alloy aluminium hcns n ufc ogns.Cmae ihas with Compared roughness. surface and di local thickness to due meas- exists the absorption in ured scatter considerable and samples received di following beam utntnadEagar and Huntington nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International Experiments h omto fakyoegetyicessthe increases greatly keyhole a of formation The 2 ae edn fatmtv lmnu los239 alloys aluminium automotive of welding Laser ae emeeg ypr lmnu n 5456 and aluminium pure by energy beam laser pulse, 9–11 4 % ffi ff nlsrwligo aluminium of welding laser on 7,8 in bu 02%hge than higher 20–25% about cient rn ufc rprtos tis It preparations. surface erent 4 2 4 tde h e the studied ae emb 03ad7039 and 5083 by beam laser 4 tde h bopinof absorption the studied h eue bopinof absorption reduced The ff 6 rnei composition in erence Wcm 4 Marsico ff 3 rnei absorp- in erence ff 3 ff rne noxide in erences − hsthreshold This cso keyhole of ects h enhanced The 2 o h CO the for 5 measured 6 2 Published by Maney Publishing (c) IOM Communications Ltd aeil ntekyoemd edn eie ne An di regime. for welding mode similar keyhole is the than energy in laser greater materials of intensities absorption at cm 0·90 kW 30 approximately at aoiaino h oaiealyn lmnsmay elements alloying volatile the of vaporisation examined. been not has the CO alloys However, the aluminium 1. to Fig. of formula in this shown of applicability as materials transfer the three energy the conditions, the welding between same e relationship the under empirical Therefore, stabilised and intensity beam laser in 0·90 to increase 0·20 from with increased absorptivity The material. hsclpoete,temaue auso energy of considerable values is measured e there transfer 1. the although di Fig. in properties, that point. shown great physical as shows focal intensity the 2 the laser Figure the Despite at di of thermal function the spot a the e as beam transfer on by energy the divided the than Therefore, of power point, by laser diameter focal the divided the the as power defined at intensity, area laser laser spot the beam as the defined irradiance, e transfer u sn oe este elaoeta required energy that the that above observed was well It formation. densities keyhole carried for power were measurements using the of out Most tin. and steel, density power threshold the reduce and keyhole the of uigCO during eurdt civ aifcoyculn between coupling alloys. aluminium satisfactory and beam achieve laser to establishment the required the by in to aid melted owing pressures, elements, easily vapour and alloying high more alloys, volatile their are The 5xxx alloys, beam. in laser 7xxx magnesium such in alloys 2090, elements zinc that in volatile lithium indicate of as results concentration These higher with 1050). and (1100 eolfreo h aoiigaos ihcne-to flsrba nryi roe ons The joints. grooved in energy beam laser of tion in concen- Katayama helpful keyhole. high is a metal of atoms, weld formation in the vaporising elements volatile the the of by tration of primarily formed force is recoil keyhole a Since increases. 5052 aeo etn,fo ayt di to easy from rated and melting, 2090 beam of laser by ease alloys aluminium of melting nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International heat measured on intensity beam laser of Effect 1 240 ffi needn ftemd fwlig rnucdO h te ad nraigwligsedalso speed welding increasing hand, other the On pronounced welding, of mode the of Independent Fuerschbach inyadlsrpwritniywsotie o oe n h bopiiyo h ae nryb the by energy laser the of absorptivity the and power for obtained was intensity power laser and ciency te,34sanessel n tin and steel, stainless 304 steel, CO for efficiency transfer < < hoe al. et Zhao 22,66,ad6N01) and 6061, (2024, 55,58,ad5182) and 5083, (5456, ffi ffi − 2 inywr on ob needn fo h workpiece the of of independent be to found were ciency 1 inywsls eedn ntelaser the on dependent less was ciency ae edn f11 te,34stainless 304 steel, 1018 of welding laser Fg ) h eut niaeta h u hnfrohraly,rsligi oe melting lower a in resulting alloys, other for than ium the that indicate results The 1). (Fig. 13 ae edn fatmtv lmnu alloys aluminium automotive of welding Laser esrdteeeg absorption energy the measured ff rne ncmoiinadta h etn e melting the that and composition in erences 2 < ae edn f1018 of welding laser ffi < inywsplotted was ciency 77 n 7N01) and (7075 21 n 3003) and (2219 ffi ut sflos onswr on ob eial o ohweld both for desirable be to found were joints follows: as cult, 13 12 2 ae edn oe n anann h ehl oeo welding of mode keyhole the maintaining and power welding laser eiwdtet emti hne,wihcudsgicnl alter significantly could which changes, geometric to the reviewed ff erent < < 13 h au of value the e r eial oaheehg etn e melting high e melting achieve increases to desirable are number dimensionless di thermal higher okic,oeaiga h aiu ae output laser maximum the at operating workpiece, n parameters ing pro- correlation proposed the data, the in scatter and temperature, workpiece, the by absorbed ie sflfaeokfrudrtnigmelting understanding for framework e useful a vides Ry e tils te,adtncudb orltdwt a with correlated be could number tin Rykalin and modified steel, stainless important another Fuerschbach welding in is processes. absorption heat energy workpiece, the evaluating in to the parameter metal base by the melt absorbed to just necessary heat e Melting efficiency Melting qaegov onswr on ob eysensitive very be to found were joints groove absorp- square than better indicating greater welds, on plate much on areas were bead of groove cross-section that square zone beam and plate, laser fusion groove same on The the bead with power. groove on square made and e groove, were the welds study absorption, To energy. can that plume plasma a of formation absorb the in result rw nsz,i bob infiataon of amount significant a absorbs workpiece. it energy, plume size, laser plasma the in when grows However, workpiece workpiece. the the with by e beam aid laser to may the the it due size of surface, in than coupling pool weld the small the material in is near plasma confined the the is and When by light. are laser absorbed original which readily photons wavelength more shorter as reradiates directions plasma The on emtycnipoeteasrto flaser of absorption the improve can geometry joint ossec n e hand, and consistency other the On absorption. beam the ffi ffi ffi ffi g utntnadEagar and Huntington iny nodrt banstsatr melting satisfactory obtain of to values high order ciency, In ciency. inyo di of ciency ciency = m = q in 14 0·48 n ffi n scatter and /( g ffi in bopino h eaitdenergy reradiated the of absorption cient a m − 2 iny hc sdfie stertoof ratio the as defined is which ciency, 18,19 D nCO in ff q 0·29 H in ff svt ftewrpeea h liquidus the at workpiece the of usivity q m rn los qain()indicates (3) Equation alloys. erent in ff ffi sdtrie ytelsroutput laser the by determined is eutn nls bopinb the by absorption less in resulting ffi a ,where ), svt hnohrcmo metals. common other than usivity D exp ffi and in s flsrba energy. beam laser of use cient inyi eemndb h weld- the by determined is ciency 2 15 and H iny oee,Fuerschbach However, ciency. ae edn f11 te,304 steel, 1018 of welding laser ato h ae emenergy. beam laser the of part a m ( − Ry 16,17 n 13 D n h hra properties thermal the and , steetap fmelting. of enthalpy the is ff q Ry/6·8) in H 4 c fjitgoer on geometry joint of ect Ry smc oe o alumin- for lower much is on httemelting the that found ...... (3) m and hwdta optimising that showed h ae nryi all in energy laser the q n lmnu a much has Aluminium . in swligspeed, welding is n − stentpower net the is r eurd Since required. are 0·17 exp ( V − ffi groove Ry/59) ciency. a 13 is V V Published by Maney Publishing (c) IOM Communications Ltd ntebs aeil h hp n ieo h edwstelws o lmnu lo ed n the and welds alloy aluminium for lowest insight the provide was can region solid adjacent the weld in the and of size behaviour. and solidification shape the the and material, pool, base the in ea.mn ftmeauedrn edn r tl evolving. still are welding during temperature of ment pyrom- radiation infrared band narrow a using lum, welding beam electron during keyhole the and in transfer butions by heat can alloys. a mode, resulting flow alloys aluminium keyhole The fluid other the pressure. of in vapour surface circu- welding welding the buoyancy, the of when by keyhole pool, driven and, results weld a is tension, and metal the of features. processes molten In of formation common pool. lation metal the molten certain the in weld alloys. within share laser resulting the as occur aluminium of processes such may vaporisation welding welding automotive significant beam density welding, of power metal. molten high the heating, For of rapid welding circulation to vigorous leads and source laser melting, heat the and metal velo- base weld metal liquid the geometry, and of temperature the of properties Measurements understanding metal. and for structure, pool prerequisite weld composition, the Therefore, in a flow stress. fluid is and residual heat of low understanding composition, and chemical modelling separately. and with microstructure, geometry, discussed welding, welds zone mode sound is fusion conduction ensure local to to desired and pertinent important weld- profiles the is laser temperature rates during mode of on cooling grow control transfer conduction inclusions depending Thus, of mass dissolve. composition, the models and pool, or as available flow, In well the weld fluid as composition. transfer, the temperature, other weldment heat of and of the interior hydrogen the thus, zinc, of and and gases, desorption tempera- magnesium and the as absorption such surface, elements pool alloying a weld welded distribution a the ture in At produced a distortion structure. cycle, and thermal stress, residual the referred often as time, to with temperature of variation The Background hrfr,teueo ihlsrpwradhigh e melting and good welding. power obtaining fusion in continuous laser helpful weld- mode is high mode. keyhole ing maintaining of conduction while speed to use welding mode the keyhole Therefore, from may shifted e speeds is welding melting high extremely decrease that found also ettase n li flow fluid and transfer Heat on efficiency melting laser of Dependence 2 nweg ftmeauepolsi h edpo h rsneo oaieeeet uha magnesium as such elements volatile of presence the pool weld the in profiles temperature of Knowledge uiglsrwlig h neato ewe the between interaction the welding, laser During edn f11 te,34sanessel and steel, stainless 304 steel, tin 1018 of welding iesols parameter dimensionless 13 ff c h rnin eprtr distribution temperature transient the ect ff ffi cstevprsto fvolatile of vaporisation the ects inyi h edn mode welding the if ciency ff cstemcotutr,uulypeerdi nuty oee,det the to due However, industry. in preferred usually microstructure, the ects Ry o CO for ffi inyin ciency 2 laser hoe al. et Zhao n ici lmnu lossgicnl decreased significantly alloys aluminium in that zinc observed and also They welds. tantalum for highest tr hi aasoe httepa temperature peak the that showed data tanta- Their and eter. steels, three alloys, aluminium several of of welding laser welding the about fusion information useful other provide from findings the fusion all Therefore, in transfer heat and flow fluid the measure- However, non-contact the for for reported techniques been Furthermore, not have pool weld the in city fields velocity and Temperature welding mode keyhole the in is processes discussion transport following of the of of much that Therefore, than ing. vigorous less is welding mode keyhole modelling of development process, is the of welding complexity conduction mode keyhole than Therefore, penetration welding. higher mode and coupling n,i aycss h acltdrslsrmi the remain values. results of calculated source the only cases, many in and, ausi fe iie ymaueetdi measurement computed by the limited of often verification is The values weld- understanding structure. systems, for The simple in ment basis rates. and, a composition cooling metal as weld velocity and serve geometry, values and computed pool complex temperature weld These predict fields, performed. can be heat calculations now accurate can and and convection conduction realistic computers both considering speed more calculations transfer high decades, calculation. of recent were availability conduction in a past the heat the of simplified As Because in a analytically. calculations to flow calculated limited heat be most cannot result, in flow convective complexity, transfer heat its of Because heat conduction. and understand to calcu- quantitative order welding. use fusion to in is recourse for lations This A especially plates. expensive, plates. the and thick in cumbersome drilled is holes placement practice the in involves thermocouples commonly of region measurement solid Temperature the developed. still in pool be weld to molten the remains measure- within the temperature of for ment technique a currently Furthermore, is available. measurement for welding procedure standardised fusion measure- during di the temperatures is surface However, of welding. ment during heat about nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International ehl oewligrslsi etrenergy better in results welding mode Keyhole Schauer ntewl ol eti rnpre yconvection by transported is heat pool, weld the In ffi ae edn fatmtv lmnu los241 alloys aluminium automotive of welding Laser utadrqie pcaie qimn,adno and equipment, specialised requires and cult tal. et 20 esrdtetmeauedistri- temperature the measured ffi culties Published by Maney Publishing (c) IOM Communications Ltd wn ovrain fbt eprtr n ops slwadtepo iei ml,tevleof value the small, is size pool the and low is transfer arise heat may of compos- mechanism which and actual temperature stress, both The of Marangoni variations conduction. to the owing as known to due forces. dominates electromagnetic of force absence tension the surface the welding, yboac,eetoantcfre n ufc e-a re fmgiue hs fteaeaevelocity average s the mm 2300 if Thus, was e magnitude. forces combined of the three order to an the due s of mm velocity 3000 and maximum 180, The ten- 9, surface were force and sion force, electromagnetic caused buoyancy, velocity by maximum the alloy aluminium 6061 of bandfrsraetnindie flows. driven Wang tension surface for obtained ntewl olaeuulymc mle hnthose than smaller much usually are pool weld the flows driven in force where electromagnetic and buoyancy both profile. pool weld shallow experimentally and the tem- wide with the determined well from agreed computed profiles boundary perature fusion The pool. saot06m iead01 mde.Tehigh The deep. mm 0·15 and wide s mm m 0·6 3 about of order is the of temper- is negative velocity results to coe The due K. flow ature 2273 outward about be radially to show found was pool weld r yia fsraetnindie o naweld a in flow driven tension surface velocities the of surface in computed typical that large are than The lower material. significantly weld base is element the this uniform, in of aluminium fairly magnesium series is of 5xxx show pool concentration of significant data the com- welding Experimental a alloys laser volatile pool. of during weld of absence that the concentration the in of is ponents pool gradient mixed spatial well a optdvlcte niaeta iigi h weld the e in highly mixing is pool that indicate velocities computed the in temperature alumin- 6063 computed of pool maximum temper- melted The and laser the ium. velocity s in computed mm fields 3000 the ature of shows velocity 3 flow Figure maximum a obtained CO o eltm eprtr esrmn r still are measurement techniques temperature reliable that time say evolving. to real this fair before is for It profile the period. on temperature time based extinguished time transient totally versus is perceived arc temperature the temperature after of pool data extrapolation of ‘measurement’ involved The technique. sn o-otc ae eetnemeasurement reflectance laser non-contact a using eprtr rfie o T edn fsm steels, some of welding GTA for profiles temperature e ilmte ie Kraus only is wide. pool millimetres weld typical few a that a fact the s m considering 0·94 of value eei h ag f05t · s velocities m 1·4 the to that 0·5 of found range the They in were camera. speed high ol ymauigtemto fprilsuiga using particles of motion weld (GTA) the arc measuring tungsten by gas pools of velocity flow surface nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International edge pool weld the and axis source velocity heat Roper temperature maximum the and the peak between Heiple surface. the pool. pool higher weld the weld the for results metal, the points pool in These weld boiling K at and 1523 weld alloy. the melting gradient 7075 to the the of higher temperature for alloy in the K the that 1353 1100 convection suggest and for the a alloy K Frequently, from 5083 2173 decreased average ition. of alloys the alloy, these maximum 7075 for on to temperatures increase 5083 of peak to alloys contents 1100 aluminium from the in moving As zinc temperature. or peak magnesium pool weld the 242 h pta rdeto ufc eso sasrs,tewl ol n te aaees eas fthe of Because parameters. other and pool, weld the stress, a is tension surface of gradient spatial The ti nw httemgiueo h eoiisfritclnt,and length, istic for velocities the of magnitude the that known is It o n Wang and Kou 2 hoe al. et Zhao 25 ae edn f66 lmnu lo and alloy aluminium 6061 of welding laser hwdta uigsainr T edn edpo,teaeaevlct scnieal lower considerably is velocity average the pool, weld welding GTA stationary during that showed ffi in fsraetnin h maximum The tension. surface of cient ffi − in.A motn osqec of consequence important An cient. ae edn fatmtv lmnu alloys aluminium automotive of welding Laser 23 1 hs eoiisaefil high fairly are velocities These . acltdtefli o during flow fluid the calculated 24 lhuhteconcentration the although − 1 22 − nawl olthat pool weld a in 1 bandsurface obtained − iha average an with , 21 1 − uiglaser During . 1 siae the estimated respectively. 13 o and Kou ff csvleof value ects − 1 . of ildpn ntevleo h eoiy h ieof size velocity the the if aluminium, velocity, of conductivity the thermal high of value the on depend will edpo a eaddb ohcneto and convection both by aided be may s m pool 0·1 weld of order the of than more is by often very velocity, maximum the than and et o yia aeo edn lmnu with aluminium welding of case typical r a For melt. pressure, constant at heat specific ao hleg ntefield. the in challenge the major of a determination in turbulence Experimental to velocities pool. lead weld high may the pools These in weld alloy. alloy aluminium aluminium 6061 of eoiisadtmeaue ntewl olremains pool weld the in temperatures and velocities easse rmtevleo h eltnumber can Peclet pool the weld of the value in the heat from assessed of be transport overall the convection and in conduction of importance relative The convection and conduction of importance Relative pool. weld the in flow heat convective of calculations eishaiyo h vial eoreo numerical of recourse available the on heavily relies dqaeeprmna ok otmoayliterature contemporary work, experimental adequate s m 2–3 of range the in weld velocities Wang mum s steel and m Kou 1 of in of calculations order the velocities the of maximum were pool the that showed n eoiyfilsi h edpool. weld the in fields velocity and etaencsayfrtecluaino temperature the liquid of of calculation and of the solutions for momentum, necessary Detailed velocity mass, a are of pool. heat provide maximum conservation weld of can the the equations in (4) of metal equation idea from rough calculated s m city 1·65 approximately 10 is ity of temperature of s est f28 gm kg 2385 of density yia au fwl olwdho m metal mm, 5 of width pool weld of value typical and respectively, source, heat y suigta tocr prxmtl halfway approximately occurs it that layer, assuming boundary a in by distribution determined velocity is Assuming that stress the from mainly results where − = sdsac ln h ufc rmteai fthe of axis the from surface the along distance is Pe ohexperiment Both 1 u eprtr coe temperature , − 3/2 m 2385 k = 3·5 = = c u u steitrailtension, interfacial the is 40 m W 94·03 d r Pe × d gm kg stevelocity, the is T c c p 10 infista h rnpr fha nthe in heat of transport the that signifies L/k d d r T − y − 4 and 3 (W , Nm k W c 1/2 p stetemlcnutvt fthe of conductivity thermal the is − 21 ...... (5) = m swdho h edpo.Fra For pool. weld the of width is 1 ffi /0·664 − − 5 K n ahmtclmodelling mathematical and 00Jkg J 1080 1 r h est n viscosity, and density the are in fsraetnind tension surface of cient u Km 3 − icst f001 gm kg 0·0013 of viscosity , K m 1 r − a eruhyestimated roughly be can , − r − 1 Pe 1 1/2 stedensity, the is n pta gradient spatial and , − , 1 h aiu veloc- maximum the , 20–22 − 1 Pe m saot54·8 about is h aiu velo- maximum The . − 1 1/2 T nteohrhand, other the On . 1 23,25 saot55 This 5·5. about is L ) stetemperature, the is K nteasneof absence the In stecharacter- the is − bandmaxi- obtained 1 − , ....(4) 1 L o welding for = c u ·0 m, 0·002 p nthe In . Pe sthe is c can / d − 26 13 T 1 Published by Maney Publishing (c) IOM Communications Ltd fha ntesldrgo svr motn o to ftePadlnme olw rmisdefinition its from follows number Prandtl the of ation di of numbers Prandtl the pool. examine for weld to and useful important solid the also the is very from It of is conductivity away thermal region heat the conduction solid of Therefore, the the dissipation that in noted the import- aluminium less be is of heat transfer also heat welding the convective of the should that for confirming for It important than alloys. more steels much of is welding convec- transport result, a heat As aluminium. tive of welding the for that eoiyo · s m 0·1 of velocity K ftewl oladsm vrg eoiy h au lo hl infiatdsrpnybtentetwo the between discrepancy significant while alloy experimental the with value well size the matched same velocity, values average the computed same For and of important. pool not weld is the of pool conduction weld heat the and in convection, is by primarily number occurs Peclet the When ieysml etcnuto acltos nih bu ettase uigwligo alu- steels of of welding during those transfer with heat alloys about aluminium Insight of properties take we case if typical a steel, For of c steels. welding of the that of with aluminium rela- of using conditions calculations. those conduction heat under simple done tively be may CO using fer alloy aluminium ( 6063 low of be pool weld laser in fields temperature and velocity Calculated 3 p − = ti fe ntutv ocmaetewelding the compare to instructive often is It Pe ae oe · W edn pe 0i min in 10 speed welding kW, 1·3 power laser 1 , 9 kg J 795 Pe o h edn fsel smc ihrthan higher much is steels of welding the for % ) n cuaecluain fha rn-teseie iesosaevr motn in important very are dimensions specimen the trans- heat of calculations accurate and 1), saot294 about is

− z values, mm y values, mm z values, mm 1 0·2 0·1 0·2 0·1 0·1 0·2 0·3 _ _ K 0 0 0 0·3 0·3 − − 1 , 1 the , L _ · · 0·3 0·2 0·1 0 _ = 0·2 0·2 u. ·0 ,and m, 0·002 Pe _ _ osdrn naverage an Considering · · · 0·3 0·2 0·1 0 0·1 · · · 0·3 0·2 0·1 0 0·1 & bandi bu 9 e 29. about is obtained ,teha transport heat the 1, r = k 05k m kg 7015 = 8Wm W 38 0·3 ms 3 ms side view 0·3 ms 3 ms top view _ 1 _ hoe al. et Zhao 3 ms − − front view − 1 x values,mm 3 1 _ y values,mm x values,mm 1 , 1 _ 1 _ 1 sartoo h ieai viscosity kinematic the of ratio a interpret- as physical The steels. and alloys aluminium steels. for than alloys aluminium for ant fsel.Teeoe ettase ycnuto smore is conduction that by transfer than heat higher Therefore, magnitude steels. of of order an nearly is alloys n iewr acltdinrn ovcin the convection, ignoring calculated were size and auswsosre o II34sanessteel, stainless 304 AISI for observed was values aluminium 1100 of welding GTA stationary for results Tbe2.Frt h hra odciiyo aluminium of conductivity comparing thermal the by First, obtained 2). (Table be also can alloys minium pool. molten the of size the determining ffi nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International 0·2 0·1 0·2 0·1 0·1 0·2 0·3 ff _ _ in o lmnu los hnwl olshape pool weld When alloys. aluminium for cient 0 0 usivity 0 ae edn fatmtv lmnu los243 alloys aluminium automotive of welding Laser 0·3 0·3 · · 0·3 0·2 0·1 0 _ _ 0·2 0·2 a . h rnt ubrpoie measure a provides number Prandtl The _ _ · · · 0·3 0·2 0·1 0 0·1 · · · 0·3 0·2 0·1 0 0·1 n otethermal the to 2 laser: 27 23 Published by Maney Publishing (c) IOM Communications Ltd ae emdfcsvle eutdi significantly in resulted values defocus di beam laser o n Le and Kou distribution density power of Effect h oe est itiuinb edn tdi at welding by distribution density power the re fmgiuelwrta hto rn heat iron, of steels. liquid that one in than than about lower is the magnitude di aluminium since of liquid Furthermore, order of boundary. the number fusion unity, Prandtl experiments than the The less near liquid much plates. of are di thicker numbers heat steel Prandtl of and the aluminium welding Since convection. stagnant, di by is by flow heat fluid of of the transport where boundary pool fusion weld the molten the Near respectively. layers, ary di and tion 01auiimaly ntermdl ne an model, of welding their for In shape alloy. pool aluminium weld 6061 the on distribution etlsuyo dYGlsrwligo 12and experi- 5182 recent of a pool. welding alloys. of aluminium laser weld 5754 Nd–YAG result large on the study and with mental deep consistent is a the focused This for produced a 4, speed, source Fig. welding in and heat shown power source As heat a size. same greatly and source shape the heat pool the for weld of nature account the to that used was e conductivity thermal nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International welds: resultant their and e relative source the heat of of profiles density power different Four 4 244 ff ff ff c fcneto.Tecluae eut showed results calculated The convection. of ect edn pe · ms mm 5·5 speed welding rn edpo hps o ie oa oe h antd n ieto fteMrnoistress Marangoni the of direction and magnitude the power total given a For shapes. pool weld erent so smr e more is usion hoe al. et Zhao ff so aegetyecestecneto rate convection the exceeds greatly rate usion ff so ntevlct n hra bound- thermal and velocity the in usion 28 ff xmndtee the examined cieeso ettasotb ovc fteha ore h s fahge oe density power higher a of use the source, heat the of convec- by transport heat of ectiveness ae edn fatmtv lmnu alloys aluminium automotive of welding Laser ffi in nlqi lmnu alloys aluminium liquid in cient ff 24 so smr motn hncnrle nodrt rdc erdcbewl pool weld reproducible produce to order in controlled than important more is usion ssoni i.5 changing 5, Fig. in shown As − 1 ff c fpwrdensity power of ect ff ce the ected ff ff ective rn h auso ufc eso safnto ftemper- of function a as tension surface of values The erent tr n opsto r motn ndetermining in important are composition and ature ocnrto fslhri te ed otiig20 containing welds steel in sulphur of concentration n 5 p fslhradlsrwle tapower a at welded laser and sulphur of ppm 150 and nsel,cnpa nipratrl nenhancing a the in significantly that was role shows penetration 6 important of Fig. depth example, an For play oxygen penetration. or weld can sulphur as steels, such in elements, amounts active small surface transfer, of heat of known mechanism well dominant now is shape It pool weld on convection of Effect alloys. aluminium of welding laser carefully during be geometry to has defocusing beam the that enables indicate and penetration deeper in results source heat f50 .Hwvr hncneto sntthe not geo- pool is the transfer, convection heat when of mechanism However, dominant W. 5200 of ere ntetosel r iia sse rmthe from seen as similar are steels two the in metries ufc eso fauiimalloys aluminium of weld tension literature. Surface aluminium the of in reported size been and not other has shape pools and the e power the on far, elements laser So the variables. welding on of power depended laser geometry a at prepared welds of cross-sections 90W hs h e the Thus, W. 1900 29 ff c fslhro h weld the on sulphur of ect htwe ovcini the is convection when that 28 ff ae oe 6 W, 860 power laser c fsraeactive surface of ect ff ce ythe by ected 24 also Published by Maney Publishing (c) IOM Communications Ltd famtlo ohtmeaueadatvt fa of activity and temperature both by expressed tension on is surface component metal the iso- of a segregation dependence adsorption of surface The solutes. Langmuir the the of and of consideration surface Gibbs and metal on of therms modelled binary adequately basis be many the can systems of solute tension active of and surface tension thermodynamics the surface Sahoo of the phenomena. model fundamentals adsorption to surface from is of alloys recourse absence compos- a the and temperature ition, In of function surface. a as pool data tension weld the on rs-etoso dYGlsrwle ·5mm 1·45 welded laser Nd–YAG of Cross-sections 5 where s hc 74auiimalyfrseveral for min alloy in 150 of speed aluminium welding values: defocusing 5754 beam thick = × s s 0 0 ln − stesraetnino h uemtla a at metal pure the of tension surface the is [1 A(T + − k a T s exp( 0 ) − − 8314T D H 0 24 834 )] /8·314T C s ae oe · kW, 3·0 power laser tal. et − 1 30 hwdthat showed hoe al. et Zhao (6) o h aclto ftesraetnino h alu- the of tension surface the of model calculation appropriate the An for systems. alloy investigated e the result little have This constituent the elements B respectively. between interactions or the alloys, A that pure indicates by binary induced and in tension and alloy additions surface the ternary of the respectively, increments of tension aluminium surface the h ae ema oigln oreadobtained and source line moving a as beam laser the oe,adwligsedbsdo etconduction heat laser on absorbed based speed width, welding seam and power, between relationship a bandfo h aafrtebnre n pure and be binaries could the alloys for these data of the aluminium tension from surface showed obtained They the Al–Zn–Mg. alumin- and that ternary two Al–Si–Mg alloys: of ium tension Goicoechea alloys surface alloys. the binary measured ternary for of available and tension are data commercial surface few very on aluminium, containing done been e little mangan- has have iron, copper alumin- silver, and of zinc, ese, lesser tension germanium, surface lead, a whereas the bismuth, ium, to reduce lithium, and, silicon, that tin, extent, observed calcium, is antimony, e It magnesium, 7. tension The Fig. surface in the investigators. on elements various high results alloying the by in of exist obtained discrepancies use wide that atmosphere. the surprising inert an involving carefully or under vacuum even conditions surface, its on controlled oxide of alumin- layer thin molten of di tension is surface ium true the However, coe ature hs oeshv enscesul sdi pre- temperature. increasing in with alloys. used ferrous of successfully tensions surface been the have dicting models These and alloy, the in oe fkyoemd ae edn.Te treated They welding. laser mode keyhole of model alloys. alumin- other investigations of and processing from beam ium electron derived and keyhole laser been both in on flow has Much fluid welding industry. and mode heat low automotive on the quality, knowledge current in seam increas- applications good found has ing its it productivity, of high and achieving distortion, low Because with thus to input. speed welding workpiece, beam heat high at the laser penetration weld the into deep enables deep welding penetrate mode Keyhole welding saturation, in point, excess factor, melting surface pure the the above the of temperatures tension at surface metal of variation the expresses temperature reference li lwadha rnfri ehl mode keyhole in transfer heat and alloys. flow aluminium Fluid is transfer of welding model heat laser and in of a flow temperature calculation Such fluid and accurate of available. for yet function important not a is as composition alloys minium hr sS rZ,Bi Mg, is B Zn, or Si is A where nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International X h ufc eso fpr lmnu decreases aluminium pure of tension surface The n17,SitHo n Gick and Swift-Hook 1973, In Al–A–B ae edn fatmtv lmnu los245 alloys aluminium automotive of welding Laser a s ffi = ffi steatvt ftesraeatv element active surface the of activity the is utt esr u otefraino a of formation the to due measure to cult in ftesraetnini negative. is tension surface the of cient X Al + D D H X 0 Al–A ff steetap fsegregation. of enthalpy the is c ntesraetninof tension surface the on ect T + 0 ,A D ff 32 c.Tog uhwork much Though ect. X hrfr,tetemper- the Therefore, Al–B sacntn which constant a is 32 X hrfr,i snot is it Therefore, Al–A–B X k 35 Al–A,B steentropy the is ....(7) omltda formulated 33 and r shown are r the are ff 31 X csof ects tal. et Al C are s 34 is Published by Maney Publishing (c) IOM Communications Ltd ic ulpntainfralwligcniin was conditions model. welding this all in for assumed penetration full since nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews of Materials tension International surface on elements added of Effect 7 density power dimensionless numbers: sionless of usually calculated is be that not could depth concern technical penetration significant The CO using theory. steel speed high S705 Bohler for geometries pool weld Spot 6 246 oesta osdrdtecniin o h forma- the for conditions the considered that models h ehl ol edtrie rmtodimen- two from of determined dimensions be the the could that on keyhole showed balance the energy They the wall. on keyhole based profile keyhole ino ehl.AdesadAtthey and Andrews keyhole. a of tion nrw n Atthey and Andrews a 99%la 7–03Ki argon in K 973–1013 at 99·99%Al min L 20 gas shielding s, 5 time irradiation etcnann 0pmS ae oe 90W; 1900 power laser S, ppm 20 containing heat hoe al. et Zhao ae edn fatmtv lmnu alloys aluminium automotive of welding Laser 36 n Klemens and 33 36 b bandthe obtained 37 5 p ,10 W; 1900 S, ppm 150 proposed − 1 argon ehiu.Temdlasmdcmlt absorption complete assumed di model finite The a using technique. source heat Gaussian moving g t Q este ftelqi n aorrespectively, vapour and liquid the of densities h eto vaporisation, of heat the stesraetnincoe tension surface the is ae evda ai o h eeomn fseveral of development it the reason, for this models. basis for subsequent a and, as zone served molten This later the equation. of and conduction cavity heat the from keyhole. model of determined the solution in was phase the distribution vapour temperature the by to The assumed only was place radiation surrounding take of melt Absorption the keyhole. in the tension, pressure surface forces hydrodynamic keyhole, between the and in balance pressure a vapour by to open due kept was the that cases, walls most question. to in Since open valid are the neglected. not predictions was for model are material assumptions used the these by and loss into heat absorbed Consequently, conduction metal. was all the that of energy vaporisation assumed surface the laser model of the because the typically However, 3 was about force. of penetration tension factor of a by depth reduced the that showed oe o ae sitdmtraspoesn iha with processing materials assisted laser for model c = 0pmS 20W; 5200 S, ppm 20 = steaclrto u ogravity, to due acceleration the is audradSteen and Mazumder Klemens T/ q/(g 37 r ga rr a bet aclt h hp ftevapour the of shape the calculate to able was 2 where , g 37 h 2 sue iclrkyoewt vertical with keyhole circular a assumed a) 1/2 d 5 p ,50 W 5200 S, ppm 150 q n iesols ufc tension surface dimensionless and 2 stepwrdniyo h beam, the of density power the is laser: 38 a ffi 29 eeoe ettransfer heat a developed steba ais and radius, beam the is in.Tercalculations Their cient. lt hcns 5mm, 15 thickness plate r and r g ff r the are erence h T is Published by Maney Publishing (c) IOM Communications Ltd hwdta h eerto nrae ihlsritn h ufc eso.Teerslsaevr important very are results These tension. surface the inten- They laser with increases Bremsstrahlung. penetration the that inverse showed considering keyhole on.Tesz ftemle olwsdtrie n 0k.I a shown was It kW. 10 and 4 absorption plasma than higher due much determined was mechanism absorption was Fresnel the boiling pool absent. by the molten were and be the reflections temperature plasma to of multiple by assumed size the when both was The than move- Furthermore, wall point. cavities the keyhole beam. to the due the cylindrical on keyhole almost of the welding. was to reflections ment that multiple concentric mode that pool found not was molten keyhole but It wall. a keyhole during the in radius pool weld keyhole They considered. the during not in were mechanism and co-workers transport pool e and absorption molten Dowden choosing heat the in convective in important guidance flow the fluid provided The theory workpiece. the be to results. found experimental the were the model where geometry with The pool comparable surface weld point. the of boiling on predictions the locations exceeded all temperature at energy of est secee,tewl eerto et osoclain ftekyoei eerto ae weld- laser penetration in keyhole the of oscillations models e shielding phen- the this to attributed does They omenon power depth significantly. this penetration increase When weld not density. the exceeded, power certain is density a to up sity of formation the to related directly from was keyhole found the that with observations well exist- mental the very pool investigations. assumed weld experimental agreed far distri- a so that yielded temperature discussed model shape beam models The this laser from the keyhole. the obtained All bution describe at the to was in source radius absorption line keyhole moving the a and and K head’ 100 ‘nail Steen approximately characteristic wall and shape. a keyhole has the pool welds at penetration temperature deep molten The conditions. considered. process the preduct were and of set in given can pressures a Mohanty for hydrodynamic geometry that keyhole data. and fairly tool hydrostatic compare experimental and software to the found Mazumder with was laser– geometry the well if pool calculated power higher The weld laser significant. at became given higher melt interaction a a vapour the be for could speed that pool scanning weld showed the in calculations velocity The interfaces. depth penetration decreasing With angle. wall hole solving work, by subsequent In obtained was equations. were Navier–Stokes components velocities horizontal The two- considered. with Only profiles. flow temperature dimensional computed the from nryasrto rcse ytepam nteo h ytmwas system the of the in plasma the by processes absorption energy be wall keyhole the of temperature the that requires the and gradient resulted tension wall liquid back surface the the at at the and balance wall to energy front the due at models weld the ditions pool in keyhole The convection thermocapillary shape, of diameter. calculations conduction pool and by weld loss depth, heat temperatures, the velocities, balanced It source. wall heat der keyhole energy. line and moving a mass the considering of and derived conservation flow equations, was of involved Navier–Stokes equations and the model balance of The energy geometry solution the keyhole. the of the keyhole the determination rotational around point for a of by conditions assumed accounted point variations models a that a existing vertical model the developed of they comprehensive Kaplan Many viscous speeds. assumptions, more welding a were these keyhole and With the keyhole around to assumed. metal the molten due of in non-viscous flow vapour vertical A forces was of tension. flux between keyhole surface vertical the and equilibrium and pressure by keyhole vapour absorbed the open was in energy kept vapour laser the the all by that assumed was ealdeeg bopinmcaimHrie tde h olpetm olwn udnlsrshut- laser sudden following time collapse the studied Herziger mechanism absorption al. et energy detailed h oeon models foregoing The ti elkonta h etclcosscinof cross-section vertical the that known well is It a n Mazumder and Kar h oesdsrbds a i o osdrany consider not did far so described models The 44 39,40 46 eeoe oest rdc h edpo et gedwl ihteeprmna data. experimental the with well agreed depth pool weld the predict to models developed rsne ealdtertclsuyo the of study theoretical detailed a presented sue lmclnrclkyoeo known of keyhole cylindrical slim a assumed 44 tal. et nertdtemdlit nitrciemtr ntemdl twsfudta h temperature the that found was It model. the in meters interactive an into model the integrated 45 obndamvn on source point moving a combined 43 35–38 39–42 n oat n Mazum- and Mohanty and ff / aoradsolid and vapour c ftepam.Terda,ail n zmta ietos Instabilities directions. azimuthal and axial, radial, The plasma. the of ect rae h icu flow viscous the treated rae nyhaigo eetoso h emisd h keyhole. the inside beam the of reflections of heating only treated 43,44 nov h tr ob qa otebiigpito h alloy. the of point boiling the to equal be to ature the involve / 41,42 liquid hoe al. et Zhao taeaenme fmlil eetosadteoverall the and reflections multiple of number average it tal. et o usdlsrwlig Klein welding. laser pulsed for uiglsrwligo rnwt ae oesof powers laser with iron of welding laser during Kaplan reflections. multiple to cylindrical more and Beck deeper of formation the to led to due absorption Fresnel multiple is welding mode Another welds. penetration deep achieve to intensities ehl radius, keyhole ihyusal uigwlig h ntblt of instability The welding. during unstable highly n.Te hwdta ehl ol silt in oscillate could keyhole a that showed They ing. Kroos keyhole. the of porosity. behaviour and dynamic spiking as such defects weld experi- However, geometry. keyhole stable a of ence radius. laser the times 1·7 least para- adjustable were keyhole the of workpiece, radius the the into and conduction heat as well as melt, tension, surface surface, keyhole the from evaporation al. et the reducing increased, angle opening keyhole the ttekyoewl xeddtebiigpitby point boiling the exceeded wall keyhole the at key- mean the of function a was reflections multiple oee,tefreblneo h ehl wall metal. the keyhole of point the boiling the on than higher balance force the However, pool weld calculated The profile. asymmetric an in di The the metal. by the absorbed power into laser the conduction that heat assumed for was formula A wall. keyhole using the speeds, at welding high at profile keyhole the low late to restricted are therefore and symmetry keyhole nryabsorption. energy onadfudta h hrceitctm constant time characteristic the that found and down nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International l h bv oesasmdkyoewl temper- wall keyhole assumed models above the All ae edn fatmtv lmnu los247 alloys aluminium automotive of welding Laser 47 50 tal. et 54–56 tde h e the studied eeoe oe nwihnon-equilibrium which in model a developed 48 aebe eeoe osuythe study to developed been have n Kaplan and r stedniyo h et and melt, the of density the is ff (r 52,53 cso utperflcin inside reflections multiple of ects 3 0 r 49 ff / c rn etcnuto con- conduction heat erent eeoe oe ocalcu- to model a developed hwdtekyoet be to keyhole the showed ) 1/2 49 where , 49 osdrdabsorption considered tal. et 49 httenme of number the that on htFresnel that found 55 r tde h free the studied 0 steinitial the is ff cielaser ective 50,51 47–49 53 tal. et Kroos Some Kar c 54 is Published by Maney Publishing (c) IOM Communications Ltd rm5 ntebs ea o4 ntefso oeo ansu nrae yaot3odr fmagni- of orders temperature 3 of about function by a increases as elements magnesium various of of vapour ures a has magnesium K, zone 1000 of fusion magnesium temperature the the a in in at 4% reduction reduction to 20% a This metal temperature. of observed. base function experiment, was strong the in a 5456 in is their welded metal 5% factor a beam In from of laser pressure alloy. of important zone aluminium fusion most the in easily the nesium weldments. be the is of reduction can strength the to Temperature tensile is leading magnesium alloy the welding, the in point, of laser rate during vaporisation pressure boiling vaporised overall vapour The low high ately. the its with that and to linearly observed Due increase is content. alloys It magnesium these 8. 5xxx of Fig. strengths some in tensile given for is content alloys series magnesium and CuMgAl elongation, correlation of formation The the cipitate. by strengthened magnesium containing are alloys series 2xxx Many liquid, phase. the auto- of strengthened constituent precipitation important some in an precipitates also is Magnesium oieauiimaly.Te6x eisaly are by alloys strengthened series precipitation 6xxx The primarily alloys. aluminium motive ouino ansu nteauiimmti.where matrix. aluminium the in magnesium solid of by strengthened solution primarily are and 0·8–5·5%Mg motn hsclpeoeat eal oexplain to able be to phenomena physical important qiiru aorpesr hnauiim hyapr ea nvcu sgvnb h Langmuir the by given is vacuum in metal pure a contain usually alloys alu- series of 5xxx welding The they laser alloys. minium aluminium, during higher vaporised much than selectively have are pressure zinc vapour and equilibrium magnesium, lithium, as nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International mode conduction and mode keyhole welding. takes both elements in alloying place of vaporisation Pronounced surface pool weld at Vaporisation E task. behaviour. major keyhole to of groups a models research is several realistic in pool develop way weld under currently the are in fields velo- city and temperature the of model compre- of mathematical unified, hensive, a of Because keyhole development welding, during laser process. processes mode physical the the of of complexities features important could pool weld from the s into ejected cm keyhole 100 melt the exceed the of part of front velocity the found calculated They the the numerically. on that beam computed humps was the the wall of than keyhole formation higher the speed, was be translation component could velocity component vector this velocity velocity translation processing di wall the the to keyhole on parallel calcu- the depending The that, drilling. conditions, melt laser showed by in place that lations take to to exceeded similar assumed wall expulsion pressure was keyhole sample the recoil the of exposed the inside propagation was and The wall tension. beam front keyhole surface laser the the the of of part to front that simulation assuming the developed the only was for behaviour wall code keyhole welding. numerical laser speed A high during propagation conditions. keyhole such and under amplitudes stable oscillations more small laser was the infinitesimally keyhole absorbed the value, at the threshold stable as If were a such formation. exceeded defects ripple power amplitudes. weld or finite cause spiking with could instabilities oscillations Such for occur could 248 ff onadMetzbower and Moon eibemdl uttk noacutalthe all account into take must models Reliable asnw n Semak and Matsunawa rn rmteba rnlto pe.When speed. translation beam the from erent hoe al. et Zhao 24,57,58 ic oaiealyn lmnssuch elements alloying volatile Since − 1 ae edn fatmtv lmnu alloys aluminium automotive of welding Laser thg ae powers. laser high at 59 60 56 ewe h esl yield, tensile the between on elto fmag- of depletion found eeoe oe for model a developed b ∞ (Mg 2 ff r-tevprsn lmn.Fra lo,tevaporisation the alloy, an For element. vaporising the pre- 2 orts i tr.Ti qainsosta h aoiainrate vaporisation the that shows equation This ature. Si) orlto ewe esl il,elongation, yield, tensile between Correlation 8 uet · t hntetmeauei increased is temperature the when atm 2·5 to pressure tude vapour the However, atm. that 0·002 figure of this from pressure observed is It 9. Fig. in given are data experimental The vapour the because rate vaporisation the elements. determining alloying all of rates vaporisation the of separ- sum calculated be can element alloying each of rate the over species species, vaporising the of pressure vapour spootoa oteeulbimvpu rsueof pressure vapour equilibrium the to proportional is ipemdlt aclt h aoiainrt of rate vaporisation the calculate to model simple A composition and Temperature equation atr fetn vaporisation affecting Factors of aluminium desirable. weldment. rates of be welding the would vaporisation alloys laser the of during in elements strength alloying reduction tensile a reason reduced main Therefore, the the be to for considered was concentration J n ansu otn o oecommercial some for alloys content magnesium and = P J M 0 R stevprsto flux, vaporisation the is (2 59 stemlclrwih ftevaporising the of weight molecular the is p stegscntn,and constant, gas the is R ) MRT − 1/2 61 o qiiru aorpress- vapour equilibrium for ...... (8) P 0 steequilibrium the is T stetemper- the is Published by Maney Publishing (c) IOM Communications Ltd nraeteoealvprsto aeo elements of significantly rate will vaporisation zinc overall or the magnesium increase of additions iimaly sasrn ucino eprtr.getyehne h rnpr falyn elements alloying of transport the of enhances circulation greatly vigorous the welding, laser temperature. During of function strong alu- a vaporis- of is overall pressure the alloys vapour found controlled vaporis- the was minium surface the It Furthermore, of pool phase. predictions rate. weld account gas realistic ation into the surrounding obtain taken the to of be order bulk in of must liquid the rate into the amounts surface recondensation workpiece. the The at the on insignificant. significant recondensed place to are elements is where takes bulk vaporised atmos- at pressure elements the elements out was from carried pheric vaporised process usually equation elements are vaporisation the operations alloying the Welding reconden- the the of where because subdivided vacuum sation in pressure They vaporisation welding. atm for 1 vaporisation derived the at overestimates rate the the equation However, Langmuir predicted pools. Langmuir weld the on correctly vapours using metal calculations dominant elements The alloying equation. the of rates pool: of weld composition the the fol- over on the vapours depending into groups alloys four aluminium lowing aluminium classified of They welding alloys. GTA during elements alloying pool. weld the from ansu,zn,adauiimae25 0 and 10, 2·5, are aluminium pure of and 2 pressures vapour zinc, the magnesium, K, 1500 of temperature lc-otnadEagar and Block-Bolten aorpesrsta lmnu.Freape ta at example, For aluminium. than pressures vapour temper- this in of magnitude of rate orders equation, three Langmuir vaporisation by the increases the from calculated Consequently, magnesium, K. 1500 to lossc smgeimi xxad6x series higher 6xxx much and have alloys aluminium 5xxx series 7xxx in in in zinc magnesium and that alloys elements as alloying 9 Fig. such alloying from volatile alloys observed important is when It many present. increased are elements significantly is range. ature qiiru aorpesr sfnto of function as pressure vapour Equilibrium 9 × ii ogl qiaetzn n magnesium and zinc equivalent roughly (iii) Eagar and Block-Bolten i)auiavpu oiae n1x series 1xxx in dominates vapour alumina (iv) h vrl aoiainrt fauiimalloys aluminium of rate vaporisation overall The i)mgeimvpu oiae n5x series 5xxx in dominates vapour magnesium (ii) eprtr o aiu elements various for temperature i icvpu oiae n5x eisalloys series 5xxx in dominates vapour zinc (i) 10 − alloys. aorpesrsaefudi xxad6xxx and 2xxx in alloys found series are pressures vapour alloys 5 t epciey hrfr,ee eysmall very even Therefore, respectively. atm 62 62 acltdvprsto Collur vaporisation calculated tde aoiainof vaporisation studied 61 hoe al. et Zhao ae ftemtl.Te proposed They metals. the of rates turbulence e opposing possible ftehg oiiyo h lcrn mn the among electrons the of mobility high the of n,fial,tetasoto h aoie species vaporised the of transport the finally, and, h otnmtldie ytesraetninforce tension surface the by driven metal molten the rates. at ation elements alloying of vaporisation intrinsic the that the of vaporisation Second, pool. weld of liquid transport the involves of step first The steps. three laser into mode conduction during vaporisation element explored. be aluminium to of yet welding have laser alloys during rate e vaporisation The melts. aluminium in cal- antimony, ium, magnesium, lead, inter- bismuth, lithium, the the of increase therefore movements vaporisation. and of local area rate surface surface The the increase liquid. to face interior the pool the of from elements active im n i,rdc h ufc eso falumin- of tension surface the reduce tin, and cium, nio n oprrsle nicesdvaporisation increased in resulted sulphur copper and and oxygen iron as in such elements active surface of ea aordet pc hree charge of space a condensation The to enhanced considered due copper. the vapour was with for metal rates consistent 80%, be vaporisation to to the 60%, in about 50%, reduction and to 10%, iron about by for rate vaporisation the reduced ehns fvaporisation of Mechanism xeiet,Sahoo experiments, plasma. the of presence rates the vaporisation conden- low in high consequently, and to The and leads ions rates ions. sation surface the charged charged than positively negatively rate the the faster between a at attraction strike surface electrons metal metal the the the since of charged surface negatively the plasma, becomes the in species various Collur metal. weld the of rate al. e et vaporisation significant a the have may on plasma a of presence highest. The the is plasma of rate Role the vaporisation near the where value axis its surface beam pool especially weld accurately, estimate to temperature essential is it Therefore, nvprsto ae fio n oprfrom copper experi- and The iron experiments. of ments vaporisation rates isothermal vaporisation on ftelqi ea ufc n euetevaporisation the reduce and rate. portion surface a metal vaporis- block liquid elements the in these of that role possible mixed is It a ation. play elements active Surface elements active surface of Role available. not are e the on nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International nauiimaly,adtoso lmnssc as such elements of additions alloys, aluminium In 63 ae edn fatmtv lmnu los249 alloys aluminium automotive of welding Laser 33 63 63,64 ssoni i.7 n oaesraeactive surface are so and 7, Fig. in shown as n Sahoo and oee,i hi stemlvaporisation isothermal their in However, tal. et ff c fpam nvprsto faluminium of vaporisation on plasma of ect 65 eeldta h rsneo plasma a of presence the that revealed 63 asdb h oeet fsurface of movements the by caused tde h ehns falloying of mechanism the studied tal. et ff tal. et cscudb u ointerfacial to due be could ects 64 tde h e the studied 64 ff cso hs lmnson elements these of ects on httepresence the that found 64 xeietldata Experimental 64 / aorinterface vapour htoeo the of one that ff ff ect. c fplasma of ect 64 nview In ff ect Published by Maney Publishing (c) IOM Communications Ltd oueo h otnwl oladtevprs-fo tils te edpos h calculations The pools. weld steel stainless vaporis- from the describe to model mathematical vaporisa- hensive the and the pool both weld changes mode, molten welding the keyhole equation. the of to Langmuir As volume mode the metal. conduction by weld predicted from the rate in the take change than not a does greatly vapour of the vaporis- bulk calculate of overall of the the down condensation to process. loss to slow ation reciable not surface used does overall pool phase be gas weld the the the can controls from vaporis- equation transport of surface Langmuir rate The the The elements. pool. weld at the plasma a ation of of vicinity presence the the the of to in due modification interface the the needed and of nature is agitation factors work surface other More as and surface welding. such elements, of active mode extent concen- surface keyhole the by welding. elements, of local coverage mode alloying that keyhole the distribution, of temperature trations include These surface variables. several not the vaporisation by its does determined surface, force is is lower recoil pool phase rate element the weld that alloying the liquid in indicated to an equal they the transported Once resulted measured, roughly vaporisation. not in was was the former transport welding elements inhibit the mode the alloying Therefore, conduction welding. in of Therefore, during molten flux the metal keyhole. in macroscale, weld mixing in convective pool vigorous a weld concen- indicating the no quite 10. within was Fig. was variation There magnesium in zone. tration of fusion shown loss the as in the pronounced pool, that trans- show weld the data of the The depth of and section width verse the along magnesium lmnu edpo.I tdigalyn lmn ftekyoesgicnl a significantly keyhole the of alloy. aluminium 5754 of the element in welding alloying Pastor faster laser studying be during In to loss pool. assumed weld be aluminium can renewal surface edn fpr rn ic h aiu o eoiyvlm fwl ol eutn nls pronounced less the Therefore, in rate. laser resulting vaporisation during in pool, iron, increase higher weld the of than of that generally than volume is alloys aluminium pool of a weld welding scan velocity the flow to maximum the width in Since beam pool iron. pure weld laser of welding the the to the for equal in distance required times 200 period about renewed time be could surface pool nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International increase. rate tion weld the that showed Calculations pool. weld 5754 the thick in mm 1·45 welded laser Nd–YAG of zone fusion in profiles concentration magnesium Typical 10 250 h omto fakyoedrn ae edn eaievprsto ae falyn elements. alloying of rates vaporisation relative welding laser during keyhole a of formation The lmnu alloy: aluminium hoe al. et Zhao tal. et ff 63 cstevprsto aeadcomposition and rate vaporisation the ects fe h lmnsaevprsd hi hrcpesr,tevprsto aeudrmost under rate vaporisation the pressure, pheric their vaporised, are elements the After 66 63

esrdtecnetainpolso oedi more of profiles concentration the measured Mg (wt-%) ae edn fatmtv lmnu alloys aluminium automotive of welding Laser ABC D 66 ae oe · W edn pe 5 nmin in 250 speed welding kW, 3·0 power laser B A 63 uiglaser during 23 h oewelding. mode the uinwligcniin s51 ie lower times 5–10 is conditions welding fusion to fpr easadtels falyn elements alloying of loss the and metals pure of ation the calculating in useful is equation the Nevertheless, data Experimental app- where place. pressures, low very at rates vaporisation change composition and rate vaporisation of Calculation during elements of vaporisation as the high as understand least to at was welding mode conduction force in recoil the Although mode. keyhole the in that to evaporation the short that and claimed thick They a rate. in vaporisation than keyhole long and slim a in aedrn ae edn.Tevnigo aorwas vapour of venting The welding. laser during rate opsto hnei h edpo uigkeyhole during pool larger weld the much in a change composition from drawn are elements pronounced more vaporised is pool weld molten the of volume Mg (wt-%) CD eRyadco-workers and DebRoy iaooadMaruo and Miyamoto ffi utadtecnesto aewshigher was rate condensation the and cult 24,58 − 1 24,57,58 57 oee,teices nthe in increase the However, 63,64 67–69 on htteapc ratio aspect the that found ff ce h vaporisation the ected hwta tatmos- at that show eeoe compre- a developed Published by Maney Publishing (c) IOM Communications Ltd agureuto.I ayisacs hna ed,wihaetpclymd thg rvlspeeds. travel high at made heat typically are low which welds, the from result such features an models These simple when theory, structures. from a instances, of obtained search many heat in values narrow is In rates by the engineer characterised vaporisation equation. than are predicted joints accurate Langmuir welded the agreement Laser more such that from are merely learned not be during to alloys. is lesson aluminium change main of composition welding The laser predicting mode in conduction useful is 01 s m (0·11 di convection that than indicating than gradient, greater rather due concentration much flux was to vapour gradient due predicted pressure The the 5182 11. Fig. to of in contours shown welding flux are vapour calculated laser the The alloy. predict the during aluminium to used at change was distribution model composition The temperature surface. pool of weld calculation ous experimentally the with agreement values. good rates determined vaporisation in calculated were The be numbers. dimen- can various sionless gradients between correlation concentration surface. using to determined condensation pool due of rates weld rates transfer the the rates and the on determine from to vaporisation phase gas of the in energy translational kinetic and momentum, equations mass, the of pool in conservation used weld of were To the locations from various surface. at escaping surface the molecules vapour from the away of e move this to include ambient vapour the force the driving the than in a for greater provides pressure pressure is excess vapour pool This pressure. weld the the higher point, of temperatures vicinity boiling At the superalloy. than aluminium, a the of of and irradiation than titanium, laser point greater during boiling points temperatures boiling the Mazumder computed and exceeds Chan reported often material. irradiated surface the temperature the peak the laser alloys, at In and transfer. metals mass of driven processing gradient pressure the of rate vaporisation temper- the pool for in calculations. used weld was account computed distribution into ature The taken were calculations. vaporisation elements to the transfer due alloying loss temperature Heat the heat surface. and of the gas pool shielding determine the weld to the to at used Navier– distribution consid- the were energy molten of of erations the solution conservation and within the equations, by transfer Stokes surface. simulated heat pool were and weld pool the flow near fluid vapour The the kin- of translational energy con- and etic of momentum, equations mass, the of servation of solution numerical involved ae oe f30k,sedo 5 nmin in 250 of speed kW, 3·0 of was value using power alloy a 5182 loss laser predicted of welding model magnesium laser a during the wt-% that 1·12 and of wt-% showed 1·16 experi- about example, data the For in zone. change mental fusion measured the was the of loss with composition magnesium agreement in calculated good than magnesium The in of greater zone. loss fusion much in the resulting was aluminium, the magnesium of hand, that of other the flux On vapour rate. vaporisation overall the oe notredmnin oicueamr rigor- more a include to dimensions three into model eety hoadDebRoy and Zhao Recently, consideration the is calculations the of feature key A − 1 ,adba aiso · m h model The mm. 0·4 of radius beam and ), ff ff c,tevlct itiuinfunctions distribution velocity the ect, so fvpr otiue otto most contributed vapors of usion 67–70 71 xeddteabove the extended nadto,mass addition, In 70 have hoe al. et Zhao − 1 edetsrcueadproperties and structure Weldment Nd–YAG for contours flux vapour Calculated 11 irsrcua features Microstructural nu n ihcoigrtseprecdi laser defined is in aluminium welded fusion experienced in zone weld rates The cooling high and input a steLnmi qaincnb trcie The attractive. calculations be the can in equation adapted Langmuir approach the as oemd edn,wihi oeatatv than attractive industry. more automotive is for welding which mode key- conduction welding, especially, mode welding, in laser hole modelling process during in vaporisation physical needed is of the work realistic much of more However, a welding. description including detailed by achieved and vapor- is calculated rate the in isation accuracy higher opposite; the ff nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International ce oe n n rie edzn micro- zone weld grained fine and zones ected ae edn fatmtv lmnu los251 alloys aluminium automotive of welding Laser otusaei cm g in are contours min aluminium in 5182 thick mm alloy: 1·0 of welding laser 71 − ae oe · W edn pe 250 speed welding kW, 3·0 power laser 1 emrdu ·0m,vle nflux on values mm, 0·40 radius beam , − 2 s − 1 67–69,71 sjust is 72 Published by Maney Publishing (c) IOM Communications Ltd 2Tpclmcotutr flsrwle 5754–O welded laser of microstructure Typical 12 seta oaodcakn n ooiy ihlsrpwrfo o7k n edn speeds welding and kW 7 to 2 from power laser with and Moon alloys, aluminium CO of Both welding Metzbower conditions. laser ing the of alloys 5xxx welded aser porosity. L and filler cracking are of parameters avoid use welding to of essential through selection composition proper Modification and metal zone. metal weld fusion the the in of occur may porosity ain bu irsrcueaecnitn ihwork with of obser- consistent are their is microstructure applications, about thickness vations automotive this in of interest material little Although alloy. 5456 eddfcssc ssldfiaincakn n loseuae riswr ossetyosre by observed consistently were grains equiaxed alloys and cracking alloy. solidification 5754–O fusion as welded the such laser of of defects zone centre Weld fusion the the in in existing zone. grains axed eoa ftepeiiae a considered was the precipitates after the structure refined of the such removal mechanical welds, the the to precipitates of harmful properties is of magnesium of depletion removal Mg and as magnesium depletion addition, In observed. of structure was grained zone fine fusion the A in sections. thinner on others by hrceiainsuisi ae emwligo a omnyosre ntefso oe Only zone. speeds. welds welding fusion high laser the at centreline in weld of the observed commonly microstructures was automotive on information published include: available The which of for is welding alloys. alloys beam microstructural aluminium aluminium laser of findings in automotive the studies describe characterisation to review edie rgntn rmtefso ieadequi- and columnar line fine fusion laser weld- of the series laser from 6xxx Nd–YAG primarily pulsed originating and consists during dendrites 5xxx cracking both alloys fication of welded zone fusion The investigated. zone Fusion been have e welding The laser 6111. Nd–YAG and and 6082, 6063, 6061, oprdwligo · mtik55– lo ihcakn a cu ln hs ekndgrain weakened these along occur may recrystal- cracking of boundaries grain the at with exist alloy commonly 5754–O thick Albright mm 1·6 and of welding Ramasamy compared for alloys an application, aluminium In of automotive welds. welding the laser of of toughness investigation increased the to tribute arwradls itntta hs npoesstae pe.Venkat speed. travel heat higher with processes welding in arc those tungsten input, than gas as distinct such less a and heat narrower the melted and partially a zone the heat melted zone, the fusion and the zone, of consisting as nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International 252 twligsedo 0 nmin in 200 laser Nd–YAG of speed cw welding kW 3 at using alloy aluminium 72–78 hoe al. et Zhao 72 2 60,72–81 iad(Fe,Mn)Al and Si h bv ento sue ntepeeto Wadtae peso pt 0 nmin in 400 to up of speeds travel and kW 3 of present the in used is definition above the iue1 hw h yia irsrcue tutrsta rgntdfo h uinln and line fusion the from originated that structures microstructures typical the shows 12 Figure 60 netgtdlsrwligo · nthick in 0·5 of welding laser investigated 03 06 21 46 74 03 oswv ae edn f5x eisalloys. series 5xxx of welding laser wave uous 6013, 5754, 5456, 5251, 5086, 5083, ae edn fatmtv lmnu alloys aluminium automotive of welding Laser ff ce oe hl h atal iheuae risi h ideo h ed The weld. the of middle the in grains equiaxed with partially the While zone. ected noeo h ale studies earlier the of one In 6 ff eentd hl the While noted. were , ce oeaegenerally are zone ected ff cso ohCO both of ects − 1 Rf 76) (Ref. 60 ocn h iudsadetci eprtr ftealloy. the of temperature eutectic and liquidus the con- to 76 76 2 ri tutr ln h eteo h uinzn in zone fusion alloy. the 6061 of welded centre laser the along structure grain s mm 8–168 mm, of 1–10 range the in thickness of plates weld to used oeo ae edd61–4alloy. alloys. 6111–T4 fusion 6xxx welded the laser in of of cracking zone welding solidification shows laser 14 Figure autogenous during aiu investigators various xeddt h eteo h uinzn.Frthese For zone. fusion the of centre the to extended h atal etdzn a eprtrsbetween temperatures has zone melted partially The below. zone melted discussed Partially be will cracking solidification to of due rates. trol speeds cooling welding high high the at pronounced more was cainlywr h qixdgan bevdnear observed grains equiaxed the were occasionally 01 s m (0·17 srwle xxalloys alloys rapidly 6xxx cooling welded the aser high cracking. L that the the for suggested to responsible were due and rates strains alloy thermal 5456 developing of ing Fuerschbach and Cieslak However, ie risrml uiglsrwlig Liquation welding. laser during remelt grains lised which phases eutectic point melting low the Therefore, edn f16m hc 74Oalyuigapower a using alloy 5754–O thick mm 1·6 of welding oueo qixdgan nrae ihincreasing with increased dendritic, micro- grains cellular equiaxed metal fine of volume be weld to cases the both in found structure They respectively. CO struc- grain equiaxed showing Microstructure 13 oiicto rcighsbe observed been has cracking Solidification oiicto rcigwsntrpre ncontin- in reported not was cracking Solidification 2 ueaogcnr flsrwl n66 alu- 6061 in weld laser of centre along ture iimalloy minium n dYGlsr sn oe f5ad3kW 3 and 5 of power using lasers Nd–YAG and 72–75,77,78,81 − 1 .Afieclua edii structure dendritic cellular fine A ). − 1 iue1 sa xml fequiaxed of example an is 13 Figure . eosrtdfieclua dendrite cellular fine demonstrated 81 72–75,77,78,81 tal. et 74,75 81 2 n dYGlsr were lasers Nd–YAG and 77 h ehns n con- and mechanism The ae edd6x series 6xxx welded Laser netgtdCO investigated ne ies weld- diverse under 79 75 bevdsolidi- observed h cracking The 60,73,76–79 2 74,75,77 laser − 1 Published by Maney Publishing (c) IOM Communications Ltd 4Sldfcto rcigaogclua dendritic cellular along cracking Solidification 14 h eta heat the httecmoiin hc r ucpil osolidi- to susceptible are which compositions the that strengthening the of b dissolution the alloys, series 6xxx a oiytecmoiino h uinzn opolm eurn ute netgto.Tee The investigation. further min requiring m 0·5 problems above speeds so travel zone at fusion the mixing the increasing by of susceptibility crack composition materials reduce filler the to of the found use modify to The can related alloys. the directly of is compositions 6xxx susceptibility as cracking. cracking solidification The to such susceptible are alloys, alloys, series aluminium automotive Many metals filler welds. is of latter Role alloys the aluminium in those welded than laser smaller welding. arc in arc tungsten region gas metal softened as gas processes such and welding densities welding metal. fusion power weld other lower in with the than in narrower a are rate heat temperature cooling the steep Consequently, high cause and welding laser gradient in speed high non-strengthening of growth and ettetbeauiimaly uha h 5xxx the as such alloys aluminium series. treatable heat riso h aeil o edn fautomotive the of in concern welding a prime For a heat is material. softening alloys, a the aluminium and of region precipitate this erties solid and in growth many occur no grain However, coarsening as and region. such alloy reactions this the phase in of occurs temperature melting eutectic the below a heat The automotive zone affected of Heat welding laser the alloys. not in aluminium is as concern small cracking line, major liquation fusion a Therefore, a the 15. only near Fig. formed in extrusions, shown was welding liquid alloy in was of used metal aluminium amount was base power 6013 the laser of of high size and grain large the very when even that rwho oso tanhree tutr o non- for structure hardened strain of loss or growth one only wide. is grains and two narrow or generally welded laser is in alloys zone aluminium melted partially The boundaries. smchrn ede fMg of needles (semicoherent ◊ hs smchrn oso Mg of rods (semicoherent phase f40i min in 400 CO of kW 3 using welded ri onayo 11T lmnu alloy aluminium 6111–T4 of boundary grain 60 ff ce oe otnn cusdet grain to due occurs Softening zone. ected o ettetbeauiimaly uhas such alloys aluminium treatable heat For ff ff ce zone. ected ce oehsamxmmtemperature maximum a has zone ected − 1 72,75,77 Rf 75) (Ref. 72 h ihpwrdniyand density power high The ff Guiterrez ce oe nlsrwelds laser in zones ected 2 ae twligspeed welding at laser 2 i as otnn in softening cause Si) 2 i n formation and Si) 72 tal. et b ff hrfr,the Therefore, ∞ c h prop- the ect precipitates 72 observed hoe al. et Zhao oiicto rcig h eainhpbtenthe between relationship The cracking. solidification o ocnrto f3 ttebto fthe of bottom the at 3% of concentration con ed n rvne rc omto.Therefore, formation. crack prevented and welds ffeig44 n 07wrswr xmndduring examined were wires 4047 and 4043 feeding of ooiy n o odre inhomogeneous powder low zone, and porosity, fusion the of of welding content during were silicon additions workpiece powder the and Although work, alloy. beam 6060–T6 their of 40 In of zone sizes alloys. particle 6080 with 150 and powders and Al–12Si and 6060 silicon thick CO added during They mm powders 4 alloys. series and 6xxx wire of filler welding laser the below. in discussed be will alloys aluminium of composi- tion the and avoid susceptibility to cracking essential solidification is level critical certain series a 6xxx above in alloys silicon of concentration the maintaining otiighge iio otn eutdi sili- a in resulted content silicon higher containing n ftefilrmtladtebs ea tthe at metal base the and metal filler the to su of attributed prevented was ing which top distribution solidification inhomo- the rapid silicon The the at bottom. the the 2% at of mac- 1% about geneity about the to from welds at decrease the of inhomogeneous to micro- be the and to probe in roscale found silicon electron of was solidification concentration Using welds the of the weld. (EPMA), at the degree analysis observed of still the min were bottom mm reduce microcracks 50 The of but to centreline. rate cracking, feed zone a found fusion at metal was the equiaxed filler of 4043 of of top number use the small of at and a mainly grains kW with consisted 4 zone dendrites of weld cellular power the a of min at m microstructure 3 plates of 6063 thick speed mm 4 of otmo h edpool. weld the of bottom aet 0 mmin mm 100 to rate CO during wires filler also 4047–WY elements. may and alloying volatile of metal of welding filler loss the the appropriate for in An compensate avoided alloys. be these can cracking fication of evidence showing Photomicrograph 15 nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International Starzer Katsuna ae edn fatmtv lmnu los253 alloys aluminium automotive of welding Laser iuto tganbudre uigwelding during boundaries grain at liquation f61–6auiimalyuig7k CO kW 7 using alloy aluminium 6013–T6 of ae t10m s mm 100 at laser m epciey eefdit h interaction the into fed were respectively, m tal. et tal. et 82 78 losuidteueo le materials filler of use the studied also − 1 tde h diino 4043–WY of addition the studied swt uoeoswls the welds, autogenous with As . − 1 − 1 n sn 07filrmetal filler 4047 using and rvlspeed travel 78 ffi nraigtewr feed wire the Increasing inywr dnie as identified were ciency 2 ae edn of welding laser 2 72 ae welding laser ffi in mix- cient − 1 high , ff ects − 1 2 Published by Maney Publishing (c) IOM Communications Ltd odce yai ertsigadas bevdmcaia rpriso h lo.Priual,over- Particularly, alloy. the of properties mechanical STEM SEM, microscopy, observed alloy. 5456 also welded laser and in testing fracture ductile tear Metzbower dynamic and Moon conducted materials. of rupture ductile coalescence microvoid nFg 7 di rupture dimple by caused failure a indicated shown as alloy, 6013–T6 17. Fig. welded in laser of zone fusion endn nple dYGlsrwle ail fsrnteigi o-ettetbealy sirre- is alloys treatable non-heat in strengthening of rapidly welded laser Nd–YAG pulsed solidified a on heat done and been zone melted partially the In the in observed commonly are failure of types These ag aee ufcs osbyascae ihtesrnt a erae yteueo h le material filler the of use strength the by tensile decreased was the strength increased However, and zone. undercutting fusion the ted the with of Guiterrez associated grains possibly columnar the di large surfaces, to a faceted adjacent had large zone fusion boundary the fusion of surface fractured h utl iperpuezn ntecnr ftealy ol epromdwtotpouigsolid- producing without performed be could alloys the increased. of speed centre of travel the width the in the as zone with decreasing rupture weld fracture, dimple of ductile type the dimple ductile a aemtladtecnr ftefso oedslydt lmnt oiicto rcigadundercutt- and cracking solidification eliminate to displayed zone fusion the The of 16. centre Fig. the in and shown metal base as direction, longitudinal the in CO di in modes n Venkat and utlt famtra n rcuemcaim ofiuaino h on lpjit utjit etc.) joint, butt joint, (lap joint the of Configuration tensile mechanism. alloy aluminium fracture impact welded and laser sur- and fracture of the material faces examined have a investigators the Several about of information ductility reveal studies Fractographic useful Fractography potentially are applications. wires production filler for the that concluded edsed fu o13mmin m 1·3 at to obtained up be zone of could speeds weld mixing weld increase Homogeneous suscepti- to crack bility. zone fusion found wire reduce and Filler contents also silicon alloys. were 6082–T6 and additions 6060–T4 of welding nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International fracture distinct two showing Fractograph 16 254 ealdmcotutrlsuisuigotcltto adnn n neln fnnha treatable non-heat of annealing and hardening tation optical using studies microstructural Detailed h rcuesraeo ae edd55– alloy 5754–O welded laser of surface fracture The 2 hrceie ylrefct erfusion near facets fracture large and boundary metal by weld of characterised centre at fracture etdi ogtdnldirection: longitudinal in tested specimen CO tensile of of regions different in modes n dYGlsrwlso 11T lo etdand tested alloy 6111–T4 of welds laser Nd–YAG and hoe al. et Zhao / odrmtlug l8e2oalloy. Al–8Fe–2Mo metallurgy powder 2 tal. et 60 ff ae edd61–4auiimalloy aluminium 6111–T4 welded laser rn ein ftetnieseiesof specimens tensile the of regions erent tal. et pcmn.Rmsm n Albright and Ramasamy specimens. 72 ae edn fatmtv lmnu alloys aluminium automotive of welding Laser 77 bevddciefatr nteIpratcagsocri di in occur changes Important the in fracture ductile observed bevdtodsic rcueatmtv lmnu los h liaestrength ultimate the alloys, aluminium automotive fracture distinct two observed 77 vrteetr edzone. weld entire the over / ff D,adTMhave TEM and EDS, rn perne with appearance, erent − 1 Starzer . 77 tal. et ductile 72,75–77 75 76 The rcagstecmoiino h lo n a degrade may and alloy the of composition the changes or 82 75 60 80 h ehnclpoete ftewl metal. weld the of properties mechanical the loscue oso okhreig hl h loss the While hardening. work of loss precipi- causes of alloys loss causes alloys treatable heat the aging to fvltl osiunsfo h uinzone fusion the from constituents volatile very of generally is ation structure zone fusion The weld. the h hra ylsa cycles thermal the esbe otwl gn fte6x losslightly alloys 6xxx the of aging post-weld versible, ntewligo xxsre alloys. series 5xxx of welding the in welds. the of elongation and fiaincakn,teueo 54filralyelimina- alloy filler 5554 of use the cracking, ification a eesr o xxad6x eisalloys series 6xxx and 2xxx ing. for quality necessary root poor to was due reduced often is weld the of rpriso h ons uiglsrwligof welding laser During joints. a the cracking, defects of humping, other properties undercuts, and of porosity, presence the and properties mechanical on welding of Effect join- alloys. and dissimilar susceptibility of cracking ing hot to related issues irsrcua nlssaenee oadesthe address to detailed needed More are analyses fractography. optical the to microstructural SEM limited of and been auto- has microscopy much welded alloys However, aluminium laser relation motive on properties. its investigation and weld microstructural weld the the evol- in with the microstructure in of insight ution significant provided studies Such 7Sann lcrnmcorp ftypical of micrograph electron Scanning 17 ff rn rmta ftebs ea.Slcievaporis- Selective metal. base the of that from erent 83–85 / rundercutting. or ue nfso zone fusion in tured rcuesraeo ae edd6013–T6 frac- welded that specimen laser tensile of alloy aluminium surface fracture hl uoeoswligo xxseries 5xxx of welding autogenous While 83–85 ff c h rgnlsrcueand structure original the ect 72 h s f44 le alloy filler 4047 of use The 83–86 ff c h mechanical the ect oee,teyield the However, ff 83–96 rn ein of regions erent ff ce zone, ected 60,80,87 Published by Maney Publishing (c) IOM Communications Ltd h nooeeu teghars h weld the across strength inhomogeneous the ihfilralyadditions, alloy geometry. filler zone with fusion all imperfect of formability the decreased showed tests alloys welding height) laser bulge (or that height dome Limiting base toughness the fracture of and Formability 34–70% were joints values. lap metal the aged of post-weld strengths e in examined joint observed were were welds conditions. and elongation strength the As in tensile alloy. when in reduction filler increase the significant moderate of a a addition the result, to a due di very metal was the base region compos- of this The hardness of significantly. ition change the not However, did zone recovery. a fusion zone heat GP the values. of to strength hardness metal the significantly base welds increased these the on treatment of aging Post-weld values range lowest the the produced to alloys in comparable series strengths 2xxx with during and welds alloy 6xxx those filler of 4047 60% welding of about butt Addition were metals. base welds the the of a of heat strengths the tensile in failed specimens tensile in occurred failure cases, elong- metal. some and base In strength the welds. tensile the of the ation increased and welds utwligo xxsre loswt 54filler 5554 with alloys series additions 5xxx content. of alloy of magnesium 90% welding higher metals about Butt with base were associated the welds being the in of those strengths tensile xxaly eepoue ih44 le alloy filler 4047 with and 2xxx produced treatable were heat the min alloys m of evaluated. the 7·0 welds were 6xxx and welds cases, to lap material many and the In butt 0·9 of Both power. thickness from laser the on varied depending speeds range from welding the in ranged powers powers with material with range lasers dioxide the the Carbon and in mm. 6082, of 2·5 to 6061, mm thickness 1·0 6060, The 6009, 5754, 6111. 5454, 5251, 5182, xxsre losfie ntefso zone. fusion the in welded failed butt alloys autogenous series from 5xxx cut specimens Tensile sections. following the properties Tensile in discussed are results The tests tear tests, tensile dynamic included tests, out bend property carried mechanical The tests welding. during loss nesium additions alloy filler autogenously both produced were cracking. avoid to additions oieauiimaly aebe eotdi the in welds reported of been auto- height have literature. welded dome alloys laser average aluminium several of motive of ratio properties higher a Mechanical had characterisation Mechanical signifi- and joints elongation. the reduced of cantly strength tensile the increased eso ha et,adpe et o a welds; welds. lap lap and butt for both for tests tests peel fatigue axial and and tests, shear tension o uoeosbt edn f6x eisalloys, series 6xxx of welding butt autogenous For 83–87 ffi inista utjoints. butt than ciencies 60,83–88 83–85 83–85 u osrs ocnrtosaiigfrom arising concentrations stress to due 83–85,87,88 83–85 a onsgnrlyrsle nlower in resulted generally joints Lap iiigdm egttests, height dome limiting hs nld:20,21,5083, 2010, 2008, include: These 60 83–85,88 lmntdudrutn nthe in undercutting eliminated –· WadN–A lasers Nd–YAG and kW 4–6·8 o utwls esl tests, tensile welds; butt for 86–88 83–85 86,87 83–85 83–85 ocmest o mag- for compensate to – Wwr sd The used. were kW 2–3 ff h xxsre losti application. this alloys series 5xxx the ihhge strength higher with rn rmta fthe of that from erent ed f5x alloys 5xxx of Welds 86 83–88 ff o ae welds laser For ff 87 ce oe The zone. ected ce oedue zone ected n ih5554 with and 83–88 h tensile The 83–87 83–87 83–85 guided 83–85 83–85 83–85 The and hoe al. et Zhao − or 87 87 1 , hrfr,epne s flsr o h edn of welding the for lasers of use expanded Therefore, h tegho a ed ne elcniin.The conditions. peel under welds lap of strength the ·5m hc heso h aematerials. same the of sheets blanks thick welded for tailored values mm the 1·25 dynamic to alloy similar were the condition dissimilar welded Furthermore, the (1·25 materials. of two weaker strengths the as the good as butt of least di at of values showed of strength 5182–O) static alloys sheets The aluminium welding. welded butt automotive laser dissimilar using from di with ness of blanks was feasibility laser tailored the the strength producing of demonstrated input higher They heat process. The low welding relatively welding. tungsten the arc to gas attributed using metal welded higher gas joints was or similar joints of butt that alloy than aluminium welded laser further. issue investigated this be industry, automotive should the by used parameter understood. alloys well treatable not non-heat is and treatable treatable heat heat between the than strength materials. peel nearly higher exhibited times alloys determine 2·5 series to 5xxx large used treatable non-heat were a tests in Peel properties joints. mechanical of e number possible of the uniformity and welds, the butt in quality high uooieauiimaly per rmsn in promising appears alloys aluminium automotive oee,cnieainwudhv ob ie othe to given di be to greater have concentration would welds. consideration stress however, lap performance higher the to fatigue owing better in welds have lap to than found are welds a greatly geometry n 01 mwr civdi h xxad6xxx and 5xxx the in respectively. achieved alloys were series laser mm autogenous 10–15 in and alloy. obtained 5754–O was welded value auto- metal For base welds, more formability. laser in better genous resulted and the welds, straining from the indicated uniform across alloys, profiles series 5xxx hardness alloys the series of zone a strength fusion 5xxx heat the the the in in strength than contrast, higher In slightly developed lowest. the was eso h edba a osdrdt edeto due be to considered was bead weld the of ness elsrnt.Jitcngrto n uinzone and fusion strength and laser configuration fatigue Joint of include strength. properties peel alloys mechanical automotive important Mg Other as such precipitates of reduction the took fracture tough- increased and The metal the coalescence. base microvoid for the by greater place for was than toughness bead the weld that showed alloy te properties Other ntae ihntefso oeweetehardness were the alloys where series zone 6xxx fusion and the 2xxx within the initiated in dome 90% limiting tests during Fractures about height metal. of base the formability of filler series that exhibited 5554 6xxx with or additions alloy 2xxx 5754–O alloy the welded than laser metal The base alloys. the of that to (Fe,Mn)Al nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International Rapp yai ertests tear Dynamic ae edn fatmtv lmnu los255 alloys aluminium automotive of welding Laser / ·5ad1·25 and 2·25 tal. et 83 ffi 6 uiglsrwelding. laser during ute novdi civn uniformly achieving in involved culties h ag di large The 88 hwdta h ttcsrnt of strength static the that showed ff 83–85 ff ce oe h rda hnein change gradual The zone. ected 86,87 c h edftgesrnt.Butt strength. fatigue weld the ect / 60 ff ·5m 6009–T4 mm 1·25 86 rn aeil 60–4to (6009–T4 materials erent 83 napouto application, production a In natgnu ed f5456 of welds autogenous in omblt f7%o the of 70% of formability a 87 ug egt f2–0mm 25–30 of heights Bulge ic elsrnt sakey a is strength peel Since ff rnei elstrength peel in erence 60 ff rn he thick- sheet erent / 12O in 5182–O) ff 2 iand Si cson ects 88 Published by Maney Publishing (c) IOM Communications Ltd etv ftehl nevl nteohrhn,we h qiiru ata rsue fN of pressures partial equilibrium The when hand, other the irres- On diameter, interval. hole hole the the in of pective increase the with linearly ooiylvl,weebt h ooiyadtecluae ausaepotdi i.1 n hyshow they and 19 Fig. in plotted are values calculated in of the formation. interest formation reducing the of and to for temperatures energies porosity contribute the free pores at standard the e the the AlN the From both high with between at librium where intervals strength levels, tensile in load, porosity e reduction explain any accelerated in may This the hardly specimen. reduction the of carried area further cross-sectional them other, in Katoh each between near resulting reduced. were zone pores further the the was when diameter, that hole strength proposed the tensile than smaller the was interval hole the usqetetamn fteabetgssduring gases ambient the of entrapment subsequent hntehl imtr h esl teghdecreased strength tensile the greater diameter, when was hole that the holes found than neighbouring was between It distance porosity. the simulate to load of to due area cross-sectional in porosity. reduction by caused porosity the when higher that is noted also porosity is the It when VPP. 3·6 MPa) than (241 ksi 35 below eswt w oe rle rnvret h direction the to transverse drilled holes two with mens The porosity). percent (volume VPP 4 to increased teghi oesvr;ti a xedtee the exceed may tensile this in severe; reduction more the VPP, is 2·5 than strength higher is level eesu oaot4VP h esl teghis strength tensile The porosity VPP. 4 by about slightly to una only up reduced is levels is level porosity strength the yield as level reduced highest be its can from bend is elongation 50% and The porosity by welds. properties weld the tensile of that static ductility found are the They to results 5086–H116 18. detrimental Their Fig. of electrodes. in 5356 performances shown with test welded bend alloy and has tensile literature. welds the aluminium Wesley in of documented e properties been alu- detrimental welded mechanical laser The on in alloys. problem common minium a is Porosity Porosity nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International test tension on porosity weld of Effect 18 256 hr r tlattopsil assfrporosity for causes possible two least at are There Katoh ff edts;1ksi 1 test; bend performance: ff ce yasalaon fprst,btdrops but porosity, of amount small a by ected hoe al. et Zhao cielaigae.prilpesrs ti lose htteequilibrium the that seen also is It pressures. partial area. loading ective 89 90 tde h e the studied 91 etdtetniesrnt f58– speci- 5083–O of strength tensile the tested n sbsdo h bopinadN and absorption the on based is One ae edn fatmtv lmnu alloys aluminium automotive of welding Laser 89 = P = ff ·9 MPa 6·895 cso edprst nthe on porosity weld of ects asdbn et F test, bend passed 89,90 ff ff c fporosity of ect cieloading ective stnand Ashton = failed ff ect 90 ata rsueo ()i uhlwrta htof that than lower much N is low N(g) very of at pressure partial formed be The can calculated. AlN be that can alloys aluminium N welding of pressures partial the to AlN, formation. required AlN for are tendency gases the reflect these and AlN of form pressures partial low codn oeutos()ad(4 niaeta very that indicate (14) and (9) equations to according oeraiyfre ntepeec faoi nitro- atomic of presence the in formed readily more edpo,tepsil ecin are reactions possible the pool, weld 1cal (1 1 edn,ntoe sasre ntemle alumin- reaction molten the the by in alloy absorbed ium is nitrogen welding, solubility The porosity nitrogen alloys. of of aluminium Solubility cause of the welding Therefore beam be welding. laser to in unlikely beam highly laser of is molecular decomposition oxygen during by stable, formed oxides be are these to alloys unlikely of is aluminium oxygen solubility in is the temperatures di formed temperatures and these and at the small pool alloys very at aluminium weld in stable the oxygen highly manganese, in are magnesium, prevailing silicon aluminium, of and oxides The oxygen section. of of following Solubility role the aluminium The in in examined porosity alloys. is of aluminium formation welds the solid in solubility gases in in these gases decrease of large type the the This of to porosity. the due in from arises resulting porosity zone, escape fusion to entrapped the be fail may in they gases temper- solidification, before lower released pool weld at the solubility If reduced atures. their cooling of subsequent because during principle, released In be hydrogen. may weld gases and these nitrogen, the oxygen, in as alloy such di absorb aluminium the may near molten pool gases the the pool, of weld composition the on Depending gases entrapment of and keyhole absorption to due the Porosity beam. of laser collapse intensity high imperfect gas the metal of by to weld generated entrapment the due induced aluminium on hydrogen bubbles based all is to Another example, prone porosity. For are process. alloys welding the × 2 D D Al(l) D D Al(l) N G G G taytmeaueidctn htANcnbe can AlN that indicating temperature any at 10 = 2 5 ° 1 ° 3 ° − (g) = =− = + + 11 ·8J.I h rsneo lsaoe the over plasma of presence the In J). 4·18 D 6 960 865 = N(g) D t- taot93K uiglsrbeam laser During K. 933 about at at.-% G N 8170 78 N(g)...... (11) 1 ° 2 − 92 (g) = D fntoe nauiimi esthan less is aluminium in nitrogen of − = AlN(s) ...... (13) ffi G + 3 ° 15·659T utt esr.Sneteoxides the Since measure. to cult AlN(s) ...... (9) ff 27·61T rn mut fabetgases ambient of amounts erent ...... (14) ...... (10) a mol cal a mol cal 2 n ()i equi- in N(g) and − − 1 1 Rf 4 (12) 94) (Ref. Rf 93) (Ref. 2 2 n N(g) and rN(g) or Published by Maney Publishing (c) IOM Communications Ltd r ihyssetbet yrgnprst during porosity alloys hydrogen its to and of susceptible aluminium point why highly melting explains are the This at aluminium K. 933 solid its higher in times that that 20 about than is and aluminium aluminium liquid temperature in in solubility decreasing hydrogen of with solubility decreases the that shows H Katayama out. ruled be of can welding beam laser alloys during nitrogen porosity AlN aluminium temperatures, of of cause lower formation the at the as stable by more mainly is pool which molten absorbed the is nitrogen by N Since temperatures. and lower at pressures AlN N(g) partial the both of values of increasing The gas. gen u a eepesdb h equation the by expressed alumin- be liquid can in hydrogen ium by of Neufeld solubility and the furnished Ransley that by found data those are reliable the ered to alu- pure according di in of vary solubility cause hydrogen minium The of primary alloys. values aluminium the of measured be welding the to during porosity considered and generally aluminium in is solubility significant has Hydrogen hydrogen of Solubility undertaken. welding be during to pool. aluminium remains hydro- still molten on molten the in nitrides of absorption inhibited the role gen the surface of by of study pool formation hydrogen comprehensive molten the of that the absorption proposed on He nitrides gas. shielding iiisi oi n iudauiima he di three at aluminium liquid and solid in bilities fauiimaly hnntoe a sda the as used was welding nitrogen laser when in alloys reduced aluminium was of porosity that reported torr 1 and torr, 760 (K), and K 273 at measured edn sta lsapaecnann h atomic the containing phase plasma a that is welding welding. of pressure partial equilibrium Calculated 19 n hti oi lmnu by aluminium solid in that and where 2 ff log log nadtoa atrt ecniee nlsrbeam laser in considered be to factor additional An rn investigators. erent ata rsue r ie nFg 0 h plot The 20. Fig. in given are pressures partial nfrigauiimntie sfnto of function as nitrogen nitride, temperature aluminium monatomic forming and in nitrogen diatomic = S S S =− =− ·3 br.Tecluae yrgnsolu- hydrogen calculated The mbar). 0·133 steslblt fhdoe (mL hydrogen of solubility the is P steprilpesr fhdoe (torr; hydrogen of pressure partial the is 26/ ) (2760/T 28/ ) (2080/T + + 2 96–104 hwtegetrsaiiyof stability greater the show D D log log mn h aaconsid- data the Among P P + − T 1·356 0·652 stetemperature the is ...(15) ...(16) / 0 Al) g 100 96 ff erent 95 who hoe al. et Zhao 95 A nlqi lmnu nevrnet fmolecular calculated of be hydrogen environments can of hydrogen in solubility atomic the and aluminium (18), liquid greatly equation in in be gas can formation gen of solubility energy aluminium free the standard data liquid the hydrogen pool. Using in atomic enhanced. weld hydrogen the of over presence of formed the be In can species gaseous 1Cluae yrgnslblt naluminium in solubility hydrogen Calculated 21 1w-p tol 3 about hydrogen. at only monatomic to aluminium at increased is wt-ppm hydrogen in 11 solubility diatomic atm the 1 hydrogen and in wt-ppm environment of 8 about is K solubility 1500 the that 0Cluae yrgnslblt naluminium, in solubility hydrogen Calculated 20 h acltdrslsaepotdi i.2.I sseen is It 21. Fig. in plotted are results calculated The nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International D D H G ae edn fatmtv lmnu los257 alloys aluminium automotive of welding Laser nevrnet fdaoi yrgnand hydrogen diatomic hydrogen of monatomic environments in ae nrslso ase n Neufeld and Ransley of results on based 2 9 ° (g) = 3550 53

wt-ppm H = H(g)...... (17) − 14·4T × 10 a mol cal 96 − 5 neuto 1)adthe and (15) equation in t ata rsueof pressure partial atm − 105 1 Rf 0)(18) 105) (Ref. faoi hydro- atomic of 96 Published by Maney Publishing (c) IOM Communications Ltd omb rcs fnceto n rwh oee,e not does e aluminium to liquid is of bubbles The tension size However, surface growth. pore hydrogen and high hydrogen nucleation beam the of smaller supersaturation, laser process much a of by the a form case and the with reduce casting process. In supersaturated cooling To increases. subsequent highly the rate in becomes hydrogen cooling absorbed pool the alumin- solid molten weld the the Therefore, ium in point. than melting aluminium the about liquid near in is liquid higher and in times temperature hydrogen 20 of with solubility decreases the aluminium above, noted As in metal bubbles weld hydrogen of iron growth and and Nucleation copper, of silicon, other. bonding the zinc, strong on to the and atoms hand aluminium one the on titanium ewe yrgnadltim ansu,and magnesium, lithium, and behaviour interactions This hydrogen attractive strong it. the between reduce to attributed iron zinc, be can whereas and aluminium copper, liquid silicon, in of solu- hydrogen presence the The of increases 22. bility titanium Fig. and in magnesium, shown lithium, aluminium are liquid results the in and solubility hydrogen on elements Anyalebechi of aluminium solubility in the hydrogen on elements alloying of Effect nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International of solubility on elements alloying of Effect 22 258 yrgni iudauiima 7 and K 973 hydrogen at of pressure aluminium partial atm liquid 1 in hydrogen

Hydrogen solubility, wt-ppm H al. et Zhao 106 a eiwdtee the reviewed has ae edn fatmtv lmnu alloys aluminium automotive of welding Laser Alloying addition,wt-% ff c falloying of ect 106 hc h loigadtosa additions These alloying understood. the well which not is formation porosity in than faster expected. much be are rates cooling as the reduced is welding, porosity hydrogen of fraction volume investigations volume, other pore Many di in porosity to hydrogen for reduction hydrogen cool- time Higher less of give rates. rates ing cooling size increasing average with decreases the that shown oln ae edt h omto fsalpores. small Fang of alloys, Mg formation Al–4·7 the of to castings For lead high Therefore, rates reduced. for is available cooling escape time and the growth rates, bubble cooling which high bubbles At hydrogen any nucleate. of escape and growth the and viscosity liquid high radius. by bubble increased small the in are bubble pool hydrogen weld a of entrapment by formation m di oendb h icst n oln aeo the of rising rate the law, cooling Stokes to and According pool. viscosity weld is molten the welding a beam by is laser governed during nucleation entrapment after for- bubble gen bubble pores of of mechanism di growth primary The the in mation. inclusions is minute metal or the imperfections of in presence nucleation aluminium the heterogeneous liquid Therefore in impractical. bubbles is hydrogen of Homogeneous bubbles. nucleation hydrogen of nucleation favour cooling of function as fraction volume Pore 23 sgvnby given is speed where ff stevsoiyo h iud h hne fporosity of chances The liquid. the of viscosity the is ff ff h oln aeo h otnwl olcontrols pool weld molten the of rate cooling The u cscnb osdrdb xmnn h a in way the examining by considered be can ects rnebtentelqi n h a ube and bubble, gas the and liquid the between erence so otoldpoes h rbblt fhydro- of probability The process. controlled usion = aei l47galloy Al–4·7Mg in rate 2r u r 2 fashrclgsbbl navsosliquid viscous a in bubble gas spherical a of sterdu ftebubble, the of radius the is ff D c falyn lmnso hydrogen on elements alloying of ect r g/(9 m ) ...... (19) 108–110 107 107 ssoni i.23. Fig. in shown as aesonta the that shown have ff c h hydrogen the ect D r stedensity the is ff tal. et s,causing use, 107 have Published by Maney Publishing (c) IOM Communications Ltd edn,a h ehl oe owr,telqi h eutn edwl o ecniuu.More continuous. be not will weld resulting success- the two between interval the if that implies liquid result the aluminium, forward, for keyhole moves the laser of keyhole mode time in keyhole the closing be porosity calculated During as can of alloys. welding, keyhole cause aluminium the of possible to welding of a due collapse as gas, considered and shielding the instability and the vapor- elements including alloying species, ised gaseous of entrapment The keyhole of collapse to due Porosity of cause welding. the beam as laser considered in alterna- be formation An macroporosity to hydrogen. has source be mechanism main not tive the may that macroporosity indicating of from sources, eliminated was possible consistently hydrogen all when was alumin- even of metal alloys, welding ium weld laser autogenous metal. the during observed in base Marsico porosity achieved. laser not severe the in is However, e this and formation. can welding porosity sources filler control gas, these the tively from are shielding hydrogen metal Eliminating weld the the in metal, hydrogen of sources solubility. hydrogen to macropores attributed The be micropores. cannot to lead may hydrogen of The the formation. in porosity e a for solubility elements concentration hydrogen hydrogen alloying in of alteration presence surfac- An alu- as acting molten by tants. energy of interfacial viscosity the and the minium, on aluminium, in elements solubility alloying of addition of Effect 24 aeascae ihlsrba edn,tepresence the welding, beam hydrogen laser cooling high with the associated for of of rate because combination However, tendency a factors. three on all the depend the may formation aid on porosity e and elements overall energy The alloying bubbles. interfacial hydrogen and the of bismuth, nucleation reduce magnesium, can lithium, lead as such shown elements is aluminium motn o bann odqaiywl.tepesr ntekyoedost h ambient the to drops keyhole. keyhole the of the collapse in the pressure for the necessary integrated time an the using calculated first modelled. been was a has keyhole of keyhole behaviour the stationary the although theoretically, formulated weld. quality the very good of CO is a root a keyhole obtaining calculations. of the for stable their important a extinction at in establishing the entrapped geometry Therefore, ing are weld. keyhole gases the cavity and 25. the of Fig. vapours space fill ation shown in to the as beam, fail laser schematically fill moving may fast to metal the behind keyhole the smoothly in the If unstable, keyhole. moves is the of wall wall wall front rear the by vacated the on metal

ff Internal friction at 700°C, cP ncnetoa edn rcse,teprimary the processes, welding conventional In h olpeo oigkyoehsytt be to yet has keyhole moving a of collapse The c falyn lmnso h icst fmolten of viscosity the on elements alloying of ect icst faluminium of viscosity Alloying addition,% 33 111 nFg 4 ufc active Surface 24. Fig. in 33 sarsl,temetal the result, a As ff cstethreshold the ects 5 112–115 eotdthat reported nearly In ff c of ect ff hoe al. et Zhao ec- 5Shmtcdarmsoigfraino void of formation showing diagram Schematic 25 rn n oprwso h re f01m.This Ducharme ms, recently, ms. 0·1 0·1 exceeds welding of laser order pulsed during the pulses ive of was copper and typical iron, The shutdown. beam keyhole laser cylindrical sudden the of following time collapse radius the keyhole calculated predicted consid- Their were negligible. was pressure be to hydrostatic to due the ered pressure the and the dynamic and flow The on fluid pressures of forces. ablation result pressure tension the a surface The be between to balance welding. mainly the considered of laser was collapse wall in the keyhole simulate keyhole to geometry a cylindrical a spherical in a of Kroos collapse Later, the bubble. for foundation theoretical Rayleigh studies, h ehl a osdrdt olpebcueof because collapse to considered was keyhole than shorter The much period a in pressure atmospheric model. pool of weld radius and keyhole initial The aluminium. and iron of welding follow- keyhole a of time collapse the calculated They nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International ae edn fatmtv lmnu los259 alloys aluminium automotive of welding Laser twl otdet mefc olpeof collapse imperfect to due root keyhole weld at Á · ie h ae emrdu.Te also They radius. beam laser the times 1·7 111 112 tal. et tal. et n Bachelor and 115 114 2 ae emdrn laser during beam laser nlddteailvari- axial the included omltdteproblem the formulated 116 twsasmdthat assumed was It 113 salse a established Published by Maney Publishing (c) IOM Communications Ltd h ehl.Teeeto emcnesl bore sudden easily a causing can liquid beam superheated electron of will this bottom The projection the through this to keyhole. moves in it as the liquid when force, preheated The of tension been 28. region surface have Fig. upper high in the the in to shown region. form due is lower to keyhole the likely upper the force in is the lower tension projection in and A keyhole, force surface the pressure of the vapour region observed the that is than It figure greater 27. of Fig. this welding in shown beam from are electron along aluminium during of pressure 1100 depth profiles vapour keyhole and calculated vapour the pressure along typical the profile tension The tension surface calculated wall. surface keyhole they the the and wall, vapour force keyhole pressure the the the position between on of Based function on balance a force. as the profile tension temperature surface measured of mainly the result and considered processes. pressure a were two wall be these keyhole to in the same on the Forces are keyhole stable omi h oe otoso h pksbecause as completely spikes region the the of collapses. fill keyhole not portions the does lower metal the molten happen spiking. in may in form process resulting The depth. periodically, keyhole in increase a containing to for pertinent conditions is the because problem welding The laser welding. beam pulse. electron laser the alloys. prevented of be aluminium shape could the of porosity improving such welding by that laser showed They pulsed in zone nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International fusion the of bottom the near porosity Matsunawa wall, of the type keyhole. keyhole at this the bubbles the keyhole gas of of the of entrapment bottom that middle in note result the may to which in interesting faster is It collapses shown is 26. times Fig. collapse in various geometry at keyhole sheet The aluminium was boundary. in moving wall a keyhole as The continuity treated equations. of wall. equation Navier–Stokes keyhole and the the involved on calculations acting The forces tension surface the CO during profiles wall Keyhole 26 260 cae n Giedt and Schauer oe W edn pe 0m s mm time beam: 10 speed at laser welding kW, sheet 2 of power aluminium extinction thick following mm 1·0 of hoe al. et Zhao ae edn fatmtv lmnu alloys aluminium automotive of welding Laser 118 118 tde ehl tblt in stability keyhole studied 118 2 tal. et od edto tend Voids ae welding laser − 117 115 1 found laser t 7Cluae ausfrsraetninpressure tension surface for values Calculated 27 8Lqi rjcinfraina oainwhere location at formation projection Liquid 28 fatmtv lmnu los sarsl,the result, depth a penetration the if As alloys alloys. welding parameter for aluminium stability higher be automotive vapour will the figure of and the lower in be tension curve will surface pressure 27 Fig. the in curve Therefore, magnesium, pressure as zinc. such to and elements due the manganese, volatile of pressures At of vapour presence presence magnesium. higher the have the as they to such time, same due elements active 1100 surface than tensions surface equi- are keyhole. the material stability the the welded and of determining in the tension parameters of important surface two pressure the vapour On hand, librium welding. mode other keyhole the penetration higher deep have during to of tends geometry value keyhole shaped narrow, The deep spiking. unacceptable exhibit to expected when However, oteisaiiyo h keyhole. due the porosity of of instability formation the to to susceptible stability more keyhole is automotive poor and of have to welding tends laser alloys aluminium Therefore, same. the are with welds for problem that a be proposed not they would data, spiking experimental their projection on liquid Based the stability where and a and forms bottom by keyhole evaluated the be could parameter formation spike ayatmtv lmnu loshv lower have alloys aluminium automotive Many cae n Giedt and Schauer ufc eso oc snal nblnewith balance force in pressure nearly vapour is force tension surface rnba edn aiya ucino cavity of elec- function as aluminium depth cavity 1100 welding beam in tron pressure vapour and S; 118 h S = stepntaindpho h keyhole. the of depth penetration the is hrfr,siigi rqetyfound frequently is spiking therefore, H/h, S S was where 118 shg o h edn fthese of welding the for high is on httetnec to tendency the that found > 118 H ·,tewl ih be might weld the 0·5, h stehih between height the is n te conditions other and S < 0·5. Published by Maney Publishing (c) IOM Communications Ltd esu esl tessi h on n a as tdwt h loigeeet ahrta,a in as than, rather elements alloying the with ated cause may There and defects. weld joint serious the most the in of cooling stresses one during cracking, tensile weld up a of sets contraction restrained The fmcoooiywr bevdi oerare some in observed were of amounts amount cases. small microporosity the although increase laser weld, of moisture not the during of did in presence gas gas macroporosity the shielding shielding that the the found in wet was as both It cause using helium welding. by main dry examined hydrogen the was and of role generation be the pore alloys, to in aluminium modes, in considered porosity conduction generally of is the hydro- gen region Since and observed. transition consistently was keyhole the macroporosity in the 5754 when conducted that between of show was data welding welding The 30. the laser Fig. several in presented during at is alloy values produced 29. Fig. defocus macroporosity in beam of shown domi- amount as size distribution, The of in porosity larger formation the or the nated mm in 0·2 Macropores the stability porosity. confirmed keyhole have of of alloys welding importance aluminium laser 5754 Nd–YAG and 5182 wave continuous during vi h rniinrgo hr h ehl sun- is minimised. keyhole be to the could where chosen porosity region stable, properly transition were the avoid parameters welding when o cracking Hot laser Nd–YAG during observed porosity Typical 29 a b eetinvestigations Recent edn f55 lmnu alloy aluminium 5754 of welding line fusion at porosity a 111 peia ooiyna otmo edpool; weld of bottom near porosity spherical hs studies These 24,66,111 24,66,111 npr formation pore on losoe that showed also b 24 reual shaped irregularly hoe al. et Zhao h aeo te,wt h rsneo o melting low of presence the with steel, of case the reported, solidi- been alloys, has aluminium cracking of fication welding fusion laser during In cracking par- welding. liquation cracking. solidifi- melting and both the liquation cracking to low susceptible cation as be of in may known liquation alloys cracking, Aluminium is place to solidification components due takes point zone as that melted the known tially of cracking solidification is during occurs whereas metal zone that cracking fusion weld cracking: weld hot the of in kinds two are defocusing beam several at produced Porosity 30 o etn on uetc uigsolidification. during associ- mainly is eutectics alloys these of point cracking Solidification melting low the and cracking, to alloys cracking, solidification various discussion of of following mechanism susceptibility a the the heat on Therefore, small focuses welds. and laser input the heat observed low been the rarely has cracking liquation rcigocr hntetemltniestrains tensile thermal Solidification displace- external alloy. and the contraction the internal of when by induced BTR occurs the of related cracking 31. extent Fig. is the in susceptibility to shown cracking as solidification Weld range solidification, temperature during brittle a (BTR) through pass alloys Most occurs: when cracking observed solidification commonly are features special Certain cracking solidification of Mechanism remedies. available etece h utlt ftewl ea within metal weld the of ductility the exceed ment xx(lM) n xx(Al–Mg 6xxx and (Al–Cu), 2xxx (Al–Mg), cracking. as 5xxx such solidification alloys of aluminium regard- Automotive mechanism proposed been the have ing theories Many BTR. the nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International ii h rc i sdull is tip crack the (iii) i)tefatrdsraei sal oee with covered usually is surface fractured the (iv) i)fatr sal cusa h ri boundaries grain the at occurs usually fracture (ii) i h rcue ufc sawy edii in dendritic always is surface fractured the (i) ae edn fatmtv lmnu los261 alloys aluminium automotive of welding Laser eima lwaeo 0 ft 200 of flowrate at helium n pe 5 nmin in 150 5754 speed of ing welding alloy: laser aluminium Nd–YAG during values thsasleyclu hrceitco unoxi- of characteristic otherwise colour metal. oxygen, silvery dised to a exposed has be it can surface it specimen the where reaches crack the if oxides nature 111 ae oe · W weld- kW, 3·0 power laser − 1 hedn a pure gas shielding , 3 h 2 − 79,117,119–121 i sal form usually Si) 1 ff ce oeof zone ected 73 u to due 123–127 while 122 Published by Maney Publishing (c) IOM Communications Ltd Matsuda utemr,sae3cudb udvddit two into narrower subdivided processes. much be cooling were could slow 2 3 other stage and Furthermore, than 1 welding stages during above the in u eprtrs nalyhstehgetsldfi eln hog eligb h eiullqi.While liquid. residual the by refilling through healing solidifi- highest the has alloy An temperatures. dus di the fteciia oiicto ag spootoa oo h eeoigcracks. developing the of to proportional is range solidification critical the of theory, generalised the to According susceptibility cracking Solidification droplets. of the form because the crack film. initiation in to was crack continuous susceptible liquid to was residual a not joint of but the propagation form 3(l) grain the stage between During in liquid at residual was lower initiated the boundaries at were because cracks 3(h) 3(l) the stage and all temperature Almost higher temperature. at 3(h) stages, nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International correspond- the curve: with susceptibility 32, Fig. cracking in into ing shown divided as was stages, process four melting solidification low The form that eutectics. alloys of susceptibility crack the by proposed theory Borland generalised The impurities. point following and during ductility metal Weld 31 262 ii tg :te‘rtclsldfiain range: solidification’ ‘critical the 3: stage (iii) i)sae4 h lo scmltl oiie:no solidified: completely is alloy the 4: stage (iv) i)sae2 nelcigo edie starts: dendrites of interlocking 2: stage (ii) i tg :a iudalyi oldblwits below cooled is alloy liquid a as 1: stage (i) rtl n oiiiaincakn temperature respectively range cracking solidification and brittle solidification: hoe al. et Zhao ff rcsdvlpa hssaedet h high the to due solid. stage the of this strength at develop cracks r ntae sarsl ftemlstrains thermal of cracks result once a possible as is initiated healing are or refilling no rsneo eiotnosntoko solid; of network semicontinuous a of presence eiullqi sdsotnosdet the to due discontinuous is liquid residual stage this at formed elayiiitdcak hrfr,n rc is moving crack no of therefore, crack; capable initiated and any refill still heal to dendrites interlocking is the between liquid residual cracking quantity large a no liquid of residual presence temperature; of the to this due mechanical occurs acquires at first strength alloy the to completely not solidified, together although mass: (the coherent join a temperature form they certain temperature), a at nucleate coherent until, crystals grow solid and temperature, liquidus rnebtentenmnllqiu n soli- and liquidus nominal the between erence 127 tal. et xlie h oiicto eaiu and behaviour solidification the explained 128 eotdta h eprtr ranges temperature the that reported ae edn fatmtv lmnu alloys aluminium automotive of welding Laser 122 T n CRrepresent SCTR and BTR 127 h magnitude the 2Efc fcntttoa etrso cracking on features constitutional of Effect 32 los –%ui lC los –·%gin 1–1·5%Mg alloys, Al–Si Al–Cu in 0·6%Si in are 1–3%Cu compositions suscepti- alloys, the crack solidification when highest bility the have alloys lM los n 1·0%Mg and alloys, Al–Mg u losi lopoessniie twsrecently was It sensitive. process also is alloys ium ucpiiiyi aiu lmnu iayaly is alloys binary aluminium given various in susceptibility e aincakssetblt hncniuu laser continuous than solidifi- Milewski and higher susceptibility Patterson much welding. crack by characterised cation is alloys ium reported ntainb taneouincmee ihcrack with competes evolution strain by initiation i.3 oamr ovn ihcomposition. rich solvent more in highest a b from to the shifted 32 has is Fig. susceptibility which a crack susceptibility. composition solidification in crack the and, resulting solidification Moreover, range depressed, higher temperature is therefore, solidification tem- alloy critical 32. solidus Fig. the wider actual in the of welding, b solidifi- perature laser non-equilibrium composition during highly i.e. the cation to widest, temperature due the critical However, its is if range susceptibility crack cation hc assahg hra tanrate, strain thermal rate gradient, high cooling stress increased a the increased to causes attributed which be can ing heat reduced segregation. the compositional to and early due input the susceptibility cracking to stainless weld contrary 304L to are 625 views observations alloy gas These of continuous steel. welding and arc pulsed tungsten comparing observation ff h oiicto rcigssetblt falumin- of 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131,132 Hot cracking susceptibility 79,119–121 nFg 3 ti bevdta aluminium that observed is It 33. Fig. in htple urn edn a decrease may welding current pulsed that stage 4 stage 1 htple ae edn falumin- of welding laser pulsed that stage 3 Composition stage 2 a–e criticaltemperature a–c coherenttemperature 121 130 2 ii lM–ialloys. Al–Mg–Si in Si ti ieyta crack that likely is It n ako refilling of lack and 130 eotdasimilar a reported 127 129 79,80,117 The Published by Maney Publishing (c) IOM Communications Ltd htrsl nahg rc ntainrt.Meanwhile, rate. initiation crack strains high shrinkage a in rates thermal result cooling that developing High fluidity. rapidly its cause by controlled is liquid h eligadhaigmvmn fteresidual the of movement healing and refilling strains, thermal with the increases rate initiation crack the losrqieueo le eassc s44 n lmnsdrn ae edn fatmtv alumin- automotive of welding laser during elements cur- procedure solidifi- and based avoid 4043 science and as unified, composition such no the metals the modify However, chosen filler carefully part, to be of may 6xxx 4047 in metal use and filler the least require 2xxx of autogenously composition while alloys at welded cracking, be alleviate, solidification can without alloys may welding 5xxx sus- turn, beam the crack welding, pulsed in solidification during during higher ature, not distribution have parameters ceptibility. on hand, density alloys, pulsing usually other 6xxx power of the are and beam high 2xxx their of industry concentrations: to magnesium due Control automotive cracking solidification alloys to the 5xxx susceptible Type in 33. sus- con- Fig. cracking used in be solidification shown should high ranges metal the ceptibility avoid weld to the trolled of composition The be materials welding can Improve cracking. measures solidification prevent following to during taken the strains thermal Therefore, of rate welding. and the magnitude laser to the alloys related and the in of closely microstructure and is cracking composition alloys chemical solidification aluminium of of welding occurrence The cracking solidification of Prevention alloys. initiated aluminium in of the susceptibility welding laser crack heal pulsed solidification responsible is increased and rate the refill cooling for higher for to a available Therefore, time liquid cracks. the residual reduce also the rates cooling high metal weld of composition chemical of Effect 33 aiu lmnu iayalloys binary aluminium various nrltv rc ucpiiiy(riae in (ordinate) susceptibility crack relative on 86–88 hrfr,i aeo otnoslaser continuous of case in Therefore, 129 hoe al. et Zhao n eitneo lmnu los te grain Other alloys. stirring, aluminium magnetic as such of techniques refining resistance crack- solidification the ing improve can elements these of speed. oscillation, iiiy n h hra rpriso h welded can displacement the or of strains properties tensile thermal Thermal the metals. and rigidity, the of metal. can structure weld zirconium solidification aluminium and the titanium resistance. refine as significantly crack such be solidification elements can Trace metal increase weld to the modified of structure solidification The structure solidification Refine alloys more. 6xxx suscepti- in or contents 2% crack silicon are low when achieved a is example, bility For cracking. cation motn nnwrdquestions unanswered Important to ratio shape aspect bead lower a weld obtain controlling and configuration, fixture welding joint proper designing by minimised be nelpia udeisedo errpshaped teardrop a of instead puddle puddle elliptical an hra tan nwligaeiflecdb the and by configuration influenced joint are input, heat welding process, in welding strains reduce can Thermal beam strains thermal refilling. pulse laser Reduce crack proper the promote that and of rate shown strain sequence been and has shape It avoid cracking. to required solidification. hot is rapid pulsing and of optimisation rates Therefore, cooling due high cracking the solidification to of likelihood power the laser the increases of pulsing However, flexibility. control uigganrfieet tas o also e It beneficial refinement. the grain has ducing welding laser Pulsed welding laser pulsed Optimise necessary. if etyeit oetrl vi h oso alloying of loss the alloys. elements. avoid ium alloying entirely of to exists loss rently the for compensate to the welding, non-autogenous In loss. element alloying temper- lower The temperature. surface the reduce can factors. adjustments and other welding laser the mode by wave of continuous possibly concentrations and local elements, surface, on pool alloying distribution temperature weld as the such determined that is factors welding known many laser is by in vaporisation the It of of welds. rate degradation the the causes of which properties problem mechanical alloys severe aluminium a automotive is vaporisation of by welding elements laser alloying during volatile of loss The loss elements alloying of of Control selection below. A presented solved. is problems satisfactorily the important been these in used not problems widely have technological is and scientific welding several industry, beam laser Although nentoa aeil eiw 99Vl 4N.6 No. 44 Vol. 1999 Reviews Materials International ae edn fatmtv lmnu los263 alloys aluminium automotive of welding Laser 141 140 yuighg etiptadlwwelding low and input heat high using by 138 n ufc cooling surface and 78,133–135 136 hrfr,saladditions small Therefore, HW), (H/W 139 ff r ihrprocess higher ers n maintaining and a lob used be also can 53,121 ff c fpro- of ect 137 beam 79,80 Published by Maney Publishing (c) IOM Communications Ltd ea 7 774· 1 1·03 611 48·6 7747 K 673 at Fe ea etn on 11 )71 38 7015 K) (1810 point melting at Fe aclt h edpo emty uhe Such geometry. pool e an weld provided the has calculate material pro- expensive. and the cess of and compre- understanding on phenomenological consuming based hensive number models time numerical large of is a Development conducting experiments adjustment by cases, of variables many by welding in obtained However, of currently error. are and variables trial welding of tions u losaejs beginning. alumin- just automotive are of alloys welding ium laser the understand la 7 602817 8·44 1076 238 2620 K 673 at Al rsneo eet uha rcsadprst,a o otcmeiieesadqaiyimprovements quality and competitiveness cost for 6 No. 44 Vol. as porosity, 1999 and cracks Reviews Materials as International such defects of presence a heat The formability and behaviour Mechanical alloying of formation. weld rates porosity improved active minimise vaporisation and surface achieve elements, the to of lower if utilised nucleation clear penetration, be the not can in is elements reduce aid It elements pores. and active hydrogen energy surface interfacial the available the sur- Third, the the by area. increases vaporisation face which of turbulence enhancing part interface and causing a surface; covering vaporising e by metal. opposing molten vaporisation two by by the elements stability alloying of a keyhole may tension they the surface Second, and the influence pattern significantly changing flow may fluid they the First, ways. poten- several can as tin a and such tially calcium, alloys antimony, aluminium lead, in bismuth, elements active Surface active surface elements of role of understanding Better of welding laser of combina- goal Acceptable important alloys. aluminium an penetration automotive full is free, welds defect the reproducible, prevent Achieving geometry pool to weld of basis Control a as serve macroporosity. of will formation of stability keyhole and A dynamics out. the the auto- carried of in been understanding porosity not of better of has compre- alloys types A cause aluminium two keyhole. motive these primary the of of the study collapse hensive is imperfect the pool caused by is weld macroporosity hydro- Furthermore, of the microporosity. release and from dissolution the gen that alloys. known aluminium is automotive important It 3·65 of an welding laser remains in goal formation porosity Avoiding formation porosity of 1080 Control 94·03 * 2385 K) (933 point melting at Al iron and aluminium of properties Thermophysical 2 Table 264 n eprtr ofiin fsraetninrespectively. tension surface † of coefficient temperature and r rmRf 144. Ref. From , k , c hoe al. et Zhao p , ff a , c h ae edn fauiimaly in alloys aluminium of welding laser the ect m Pr , ff Pr r eie quantities derived are ce oe oso loigeeet,the elements, alloying of loss zone, ected , s n d and , ae edn fatmtv lmnu alloys aluminium automotive of welding Laser ff s/ c h aoiainrtso the of rates vaporisation the ect d T ersn est,temlcnutvt,seii et hra ifsvt,vsoiy rnt ubr ufc tension, surface number, Prandtl viscosity, diffusivity, thermal heat, specific conductivity, thermal density, represent gm kg r , − 3 Wm k , † − ff 1 ff cs inhibiting ects: K ciewyto way ective − 1 ff c Jkg rsto orts p 9 6·80 795 , − 1 K − 1 a m Outlook h rcs navr arwoeaigrgo.This region. operating narrow very optimising a than in technology important process this of more the use is broader the the environment occur to manufacturing in commonly the a which process disturbances increasing in the the on of of presence robustness Research and needed. predictability are variable process larger windows industry, automotive the in use oi a o enaeutl drse odt for date to addressed adequately been not has topic h edn fatmtv lmnu alloys. aluminium automotive of welding the lo alrwle lnsadohrautomotive need internal other the by and both aluminium driven blanks welded be will laser welded their components of tailor reliable, use alloy more Enhanced expected are grow. and the industry to automotive As expensive the understood. in less applications poorly get been welding lasers has laser preferred aluminium date, the to of is of However, welding method. use Laser fabrication require blanks. will welded bodies tailor automobile in aluminium bodies. automobile expanded in materials for lightweight push of jointly use as industry timely and particularly signifi- is government manufacturing These investigation their and addressed. and design be cance, major to have and remain key issues issues several structure, However, and composition, alloys. problems welded geometry, the of as the properties welding to in as led processes the have physical well the sciences at into applied insights investigations and new basic particular, alu- of automotive In crossroads of alloys. welding in minium made laser been the has progress understanding significant years, recent In a have properties. often joint parameters on impact processing major Small of process. in welding robust particularly laser variations a that not indicated is has aluminium date to Research robustness Process of aluminium availability hydroformed the information. on this future, tailored particularly the welded depends structures laser in aluminium, aluminium and, welded of laser blanks adoption are of the use improvement wider as formability to formability on critical Better also research needed. and much mechan- control data are to ability An properties the and ical joints. whole a alloy as properties joints mechanical of aluminium the of welded understanding improved laser sag, root of undercut, ability a (e.g. all geometry bead etc.) weld as well , 2 s aigtems egtadcs e cost and weight most the Making − × × × × 1 * 10 10 10 10 l aafo e.13uls indicated; unless 143 Ref. from data all : − − − − 5 6 5 5 ff c h ehnclbhvoradform- and behaviour mechanical the ect m gm kg ...... ·0501 1·872 0·12 0·0055 ...... ·030050·914 0·015 0·0013 , − 1 s − 1 Pr s Nm ,d 142 − 1 o widespread For ff Nm − − cieueof use ective s/ 4·9 3·5 d − T × × 1 , K 10 10 − 1 a − − 4 4 and Published by Maney Publishing (c) IOM Communications Ltd n rS .Dvdfrteritrs nti work. this in References interest their Abraham for P. David K. A. S. Professor Dr thank and DE-FG02–96ER4 authors the The (grant by Energy 5602). provided of was Department work US this for support Financial Acknowledgement related energy and increas- the environmental with regulations. comply stringent to push ingly external the by and 30. 29. 28. 27. 26. 25. 24. 23. 22. 20. 21. 19. 18. 17. 16. 15. 14. 13. 12. 11. 10. 31. 35. 34. 33. 32. 2. 1. .‘edn asrauiim,2den 98 aln,CA, Oakland, 1978, edn; 2nd aluminium’, Kaiser ‘Welding 9. 3. 4. 8. 7. 5. 6. . ., . , . . 1996, , J., . , . , .  . 1996. Canada, .: . ., ., 67 . . , . . . .,  . , . 1999, J., . , . , .  . Metals : 1982, . 489–520; . David), ASM. A. OH, S. Park, (ed. States’, United the in . , ., . . , . . .  . . 1978,  . 917. (3), .  . . Dekker. Marcel York, New e.L .Rdimk n .A rmr) 6–0;1989, 169–206; Cremers), A. 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