Materials Transactions, Vol. 47, No. 5 (2006) pp. 1275 to 1285 #2006 The Japan Institute of Metals OVERVIEW
Developments and Applications of Bulk Glassy Alloys in Late Transition Metal Base System
Akihisa Inoue, Baolong Shen and Akira Takeuchi
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
We review our recent results of the formation, fundamental properties, workability and applications of late transition metal base bulk glassy alloys which have been developed after the first synthesis of Fe-based bulk glassy alloys by the copper mold casting method in 1995. The late metal transition base bulk glassy alloys were obtained in Fe–(Al,Ga)–(P,C,B,Si), Fe–(Cr,Mo)–(C,B), Fe–(Zr,Hf,Nb,Ta)–B, Fe–Ln– B(Ln=lanthanide metal), Fe–B–Si–Nb and Fe–Nd–Al for Fe-based alloys, Co–(Ta,Mo)–B and Co–B–Si–Nb for Co-based alloys, Ni–Nb– (Ti,Zr)–(Co,Ni) for Ni-based alloys, and Cu–Ti–(Zr,Hf), Cu–Al–(Zr,Hf), Cu–Ti–(Zr,Hf)–(Ni,Co) and Cu–Al–(Zr,Hf)–(Ag,Pd) for Cu-based alloys. These bulk glassy alloys exhibit useful engineering properties of high mechanical strength, large elastic elongation and high corrosion resistance. In addition, Fe- and Co-based bulk glassy alloys have good soft magnetic properties which cannot be obtained for conventional amorphous and crystalline type magnetic alloys. The Fe- and Ni-based bulk glassy alloys have already been used in some application fields. These late transition metal base bulk glassy alloys are promising as new metallic engineering materials. [doi:10.2320/matertrans.47.1275]
(Received January 10, 2006; Accepted March 30, 2006; Published May 15, 2006) Keywords: synthesis, applications, bulk glassy alloys, late transition metal base, mechanical properties, soft-magnetic properties
1. Introduction 2. Features of Alloy Components in Late Transition Metal Base Bulk Glassy Alloys Since the first syntheses of bulk glassy alloys in metal- metal alloy systems without metalloid elements through It is well known that the first synthesis of late transition stabilization of supercooled liquid1–3) for several years metal base bulk glassy alloy containing more than 50% late between 1988 and 1992, great efforts have been devoted to transition metal was made for Fe–(Al,Ga)–(P,C,B) system in search for new bulk glassy alloy systems with high glass- 1995,8) followed by Co–Ga–(Cr,Mo)–(B,C,P) in 1996,14) Ni– forming ability and useful functional properties and to clarify Nb–(Zr,Ti,Hf)–(Co,Fe,Cu,Pd) in 199925) and then Cu– the origins for high stability of supercooloed liquid against (Zr,Hf)–Ti in 2001.20) It is thus noticed that all the late crystallization and for the appearance of unique properties for transition metal base bulk glassy alloys were developed for bulk glassy alloys.4–7) A majority of studies on bulk glassy the last one decade after 1995. alloys have been focused on early transition metal base alloys Table 1 summarizes typical bulk glassy alloy systems in Zr-, Ti- and Hf-based systems, lanthanide metal (Ln) base containing more than 50 at % late transition metal as a main alloys, simple metal base alloys in Mg- and Ca-based systems constituent component. These alloy systems can be divided and noble metal base alloys in Pd- and Pt-based systems.4–7) into two groups of metal-metalloid and metal-metal types. Considering some basic factors such as novel properties, The former type alloys were mainly obtained in Fe-, Co-, Ni-, material cost and material deposits on the earth for future Pd- and Pt-based systems, while the main latter type alloys development of bulk glassy alloys as advanced engineering were synthesized in Ni- and Cu-based systems. It is also materials, it was extremely important to find a late transition noticed that Ni-based bulk glassy alloys can be formed rather metal base bulk glassy alloy which had not been synthesized easily in both alloy types. When we focus on main ternary before 1995. Under the above-described severely limited systems in Fe-, Ni- and Cu-based alloys which can be situation of bulk glassy alloy systems, we succeeded in regarded as important engineering systems, one can see Fe– fabricating Fe-based bulk glassy alloys in Fe–Al–Ga–P–C–B (Al,Ga)–metalloid, Fe–(Cr,Mo)–(C,B), Fe–(early transition system in 1995.8) Since then, we have also synthesized a metal)–B, Fe–Ln–B, Fe–(B,Si)–Nb, Ni–Nb–(Ti,Zr,Hf), Cu– variety of Fe-based bulk glassy alloys,9–13) followed by Co- Ti–(Zr,Hf) and Cu–Al–(Zr,Hf) systems. Table 1 also indi- based bulk glassy alloys,14–16) Ni-based bulk glassy al- cates that a more variety of bulk glassy alloys can be loys17–19) and then Cu-based bulk glassy alloys20–24) through fabricated by adding fourth and fifth elements to the basic alloy searches on the basis of the three empirical component ternary alloys. On the other hand, the metal-metal type alloys rules for stabilization of supercooled metallic liquid.4–6) It has in Fe- and Co-based alloy systems do not have high glass- subsequently been found that the late transition metal base forming ability and their critical diameters lie in the range of bulk glassy alloys exhibit various unique properties which 1.0 to 1.5 mm. The future development of Fe- and Co-based have not been obtained for any kind of crystalline alloys. The alloys with various alloy components in the metal-metal type novelty of various properties for late transition metal base is important for further extension of application field of bulk bulk glassy alloys has enabled us to use as engineering glassy alloys. materials and their application fields have a tendency to be The feature of three metallic components in the basic extended widely. This paper intends to review our recent ternary alloy systems can be divided into five groups, as results on the formation, properties, thermal stability, work- summarized in Table 2. Group I consists of late transition ability and applications of late transition metal base bulk metal, simple metal and early transition metal as exemplified glassy alloys. for Cu–Zr–Al and Cu–Hf–Al systems, group II includes late 1276 A. Inoue, B. Shen and A. Takeuchi
Table 1 Typical bulk glassy alloy systems in late transition metal base containing more than 50 at % late transition metal reported up to date.
Base Metal Metal-Metalloid Metal-Metal Fe–(Al,Ga)–(P,C,B,Si) Fe–Ga–(P,C,B,Si) Fe Fe–Ga–(Nb,Cr,Mo)–(P,C,B) (Los Alamos) Fe–Nd–Al Fe–(Cr,Mo)–(B,C) Fe–Ln–B, Fe–(Zr,Hf,Nb,Ta)–B, Fe–(B,Si)–Nb Co–Ga–(Cr,Mo)–(P,C,B) Co–Nd–Al Co Co–(Zr,Hf,Nb,Ta)–B Co–Sm–Al Co–Ln–B Ni–Nb–Ti, Ni–Nb–Zr, Ni–Nb–Hf Ni–(Nb,Cr,Mo)–(P,B) Ni–Nb–Zr–Ti Ni–(Ta,Cr,Mo)–(P,B) Ni–Nb–Zr–Ti–M (M=Fe,Co,Cu) Ni Ni–Zr–Ti–Sn–Si (Yonsei Univ.) Ni–Nb–Hf–Ti Ni–Pd–P Ni–Nb–Hf–Ti–M Ni–Nb–Sn (Cal Tech) Cu–Zr–Ti, Cu–Hf–Ti Cu–Zr–Ti–Ni, Cu–Hf–Ti–Ni Cu–Zr–Ti–Y, Cu–Hf–Ti–Y Cu–Zr–Ti–Be, Cu–Hf–Ti–Be Cu–Pd–P Cu Cu–Zr–Al, Cu–Hf–Al Cu–Ni–Pd–P Cu–Zr–Al–M, Cu–Hf–Al–M (M=Ni,Co,Pd,Ag) Cu–Zr–Ga, Cu–Hf–Ga Cu–Zr–Ga–M, Cu–Hf–Ga–M Cu–Zr–Al–Y (Cal Tech) Pt–Cu–P Pt Pt–Cu–Co–P (Cal Tech) Pt–Pd–Cu–P Pd Pd–Cu–Ni–P
Table 2 Feature of three metallic components in ternary base systems Table 3 Features of glass-forming ability, temperature interval of super- where bulk glassy alloys are formed by the copper mold casting method. cooled liquid and reduced glass transition temperature for late transition metal base bulk glassy alloys. ETM: Early Transition Metal I Cu-Zr-Al, Cu-Hf-Al LTM: Late Transition Metal Fe-(B,Si)-Nb, Fe-Nb-B Glass-Forming Ability Ln: Lanthanide Metal II Fe-Zr-B, (Fe,Co)-Ln-B Base Metal > 50 at% (Co,Fe)-Ta-B Alloy Type Fe Co Ni Cu Pd Pt ≥ Fe-(Cr,Mo)-(C,B) *; dmax 30 mm, ETM>Ti>LTM ≥ ETM III Fe-(Al,Ga)-(P,C,B) Metal-Metalloid * * ; dmax 5 mm ; Ti (Zr,Hf,Nb,Ta) ; d ≥ 3 mm, Ni-Nb-Ti, max Ln IV Metal-Metal - - - - ; d < 3 mm Ln,ETM>LT Cu-Zr-Ti, Cu-Hf-Ti max IV Ni-Pd-P, Cu-Pt-P GFA: Pd Pt >> Cu > Ni > Fe > Co V Pd-(Ni,Cu)-P, (Pd,Pt)-Cu-P ∆ M>Metalloid Temperature Interval of Supercooled Liquid ( Tx) Base Metal > 50 at% Alloy Type Fe Co Ni Cu Pd Pt ∆ > ; Tx 90 K, ∆ = I LTM II Metal-Metalloid ; Tx 60 ~ 90 K, ∆ < Fe,Co, Pd,Pt ; Tx 60 K Ni,Cu Metal-Metal - - - - Ln,ETM>Al,Ga>LTM III V ∆ Tx : Cu > Fe ; Ni ; Pd ; Pt > Co Al, III Met- Reduced Glass Transition Temperature (T /T ) Ga,Sn Al,Ga>LTM>Metalloid alloid , x l Base Metal ≥ 50 at% Pd >LTM>Metalloid ≥ : ∆H < 0 Pt Alloy Type Fe Co Ni Cu Pd Pt *; Tx/Tl 0.70, ∆ ≥ : H ≥ 0 Metal-Metalloid * ; Tx/Tl 0.65, ≥ ; Tx/Tl 0.60, Metal-Metal - - - - < ; Tx/Tl 0.60 transition metal, metalloid and early transition metal or Ln such as Fe–(B,Si)–Nb, Fe–(Zr,Hf,Nb)–B, Fe–Ln–B and Fe– stabilization of supercooled liquid as compared with the (Cr,Mo)–(C,B) systems, group III is composed of Fe, metal- negative heat of mixing factor. loid and Al or Ga, group IV is exemplified for Ni–Nb–Ti and Table 3 summarizes the features of glass-forming ability, Cu–(Zr,Hf)–Ti systems and group V consists of Ni–Pd–P supercooled liquid region and reduced glass transition and Cu–Pt–P systems. Considering that bulk glassy alloys are temperature for late transition metal base bulk glassy alloys. formed in all types of the basic ternary systems, it can be said The glass-forming ability is the highest for Pd- and Pt-based that the atomic size mismatch factor is more dominant for alloys, followed by Cu-, Ni-, Fe- and then Co-based alloys. Developments and Applications of Bulk Glassy Alloys in Late Transition Metal Base System 1277
Table 4 Features of static mechanical strength and compressive ductility for late transition metal base bulk glassy alloys.
Static Mechanical Strength ≥ Alloy Type Fe Co Ni Cu Pd Pt Base Metal 50 at% σ ≥ *; f 5000 MPa, Metal-Metalloid * σ ≥ ; f 3000 MPa, σ ≥ Metal-Metal - - ; f 2000 MPa, ; σ < 2000 MPa σ f Strength ( f): Co > Fe > Ni > Cu > Pd > Pt Compressive Ductility
Alloy Type Fe Co Ni Cu Pd Pt ε *; f = 0.02 Metal-Metalloid * * * * * + plastic strain ε Metal-Metal * * - - ; f ; 0.02, ε ; f = 0.017~0.02, Ductilty: Cu ; Ni > Pd ; Pt ; Fe > Co ε ; f < 0.017
Fig. 2 Compositional dependence of supercooled liquid region ( Tx) for [(Fe1 x yCoxNiy)0:75B0:2Si0:05]96Nb4 glassy alloys.
Fig. 1 Compositional dependence of glass transition temperature (Tg) for [(Fe1 x yCoxNiy)0:75B0:2Si0:05]96Nb4 glassy alloys.
There is a tendency for glass-forming ability to increase with decreasing liquidus temperature of their ternary alloys. In addition, we can notice a rather close relation between glass- forming ability and Tg=Tl or Tx, though their orders do not agree completely. Fig. 3 Compositional dependence of maximum sample diameter (Dmax) Table 4 also summarizes the features of mechanical for [(Fe1 x yCoxNiy)0:75B0:2Si0:05]96Nb4 glassy alloys. fracture strength ( f) and compressive ductility ("f) for the late transition metal base bulk glassy alloys. All the late 3. Formation and Fundamental Properties of Fe- and transition metal base bulk glassy alloys in metal-metalloid Co-based Bulk Glassy Alloys in (Fe,Co,Ni)–(B,Si)–Nb type have good elastic ductility as is evidenced from the System achievement of 2% elastic strain. On the other hand, the 2% elastic strain property for the metal-metal type alloys is We have found that the addition of small amounts of Nb to limited to Ni- and Cu-based alloy systems. The 2% elastic (Fe,Co,Ni)–(B,Si) alloys is very effective for the increase in strain property has been also recognized for other bulk glassy glass-forming ability through the increase in the stability of alloys such as Zr-based alloy systems and is an essential supercooled region against crystallization.13) The glass factor for the achievement of high fracture strength. transition phenomenon can be observed over the whole As is evident from the development history of Fe- and Co- composition range in [(Fe1 x yCoxNiy)0:75B0:2Si0:05]96Nb4 based bulk glassy alloys, only a few alloy systems of alloys. Figure 1 shows the compositional dependence of (Fe,Co,Ni)–Nb–(B,Si) and Co–Fe–Ta–B were developed for glass transition temperature (Tg) of the (Fe,Co,Ni)–B–Si– the last three years after the RQ11 conference held in 2002. 4%Nb glassy alloys. The Tg shows a significant change with Therefore, we will describe firstly the formation and Ni content and decreases almost linearly from 810 K to 760 K fundamental properties of these new Fe- and Co-based bulk with increasing Ni content. There is no distinct difference in glassy alloys in the next two chapters. Tg with the concentration ratio of Co to Fe. 1278 A. Inoue, B. Shen and A. Takeuchi
Fig. 4 Outer shape and X-ray diffraction patterns of [(Fe1 xCox)0:75B0:2Si0:05]96Nb4 glassy alloy rods.
Fig. 6 True stress-strain curves of [(Fe0:8Co0:1Ni0:1)0:75B0:2Si0:05]96Nb4 and [(Fe0:8Co0:2)0:75B0:2Si0:05]96Nb4 glassy alloy rods with a diameter of 2 mm.
Fig. 5 Compositional dependence of compressive fracture strength of [(Fe1 x yCoxNiy)0:75B0:2Si0:05]96Nb4 bulk glassy alloy rods produced by the copper mold casting method. further increase in Ni content causes the decrease in strength to about 3700 MPa. In the case of the same composition of B, Si and Nb elements, the fracture strength is the highest for the The supercooled liquid region ( Tx) defined by the Fe-based alloy, followed by the Co-based alloy and then the difference between Tg and crystallization temperature (Tx) Ni-based alloy. In addition to the high strength, the Fe–Co– shows a maximum value of about 65 K in the range of 0.50– Ni–B–Si–Nb alloy rods also exhibit distinct plastic strains up 0.65Fe, 0.35–0.45Co and 0 to 0.15Ni and keeps rather high to about 0.5% before final fracture as exemplified in Fig. 6. values of over 60 K in the Ni content range up to about The alloy rod subjected to the plastic strain up to 0.3% shows 0.35Ni, as shown in Fig. 2. In the alloy composition range, a distinct shear band along the maximum shear stress plane. we can obtain high reduced glass transition temperatures Besides, we can observe the trace of viscous flow deforma- above 0.61 as well as high glass-forming ability leading to tion on the shear band, indicating the significant increase in the formation of bulk glassy alloys with diameters up to at temperature in the shear band. least 5 mm by the copper mold casting process, as shown in These Fe–Co-based glassy alloys also exhibit good soft Fig. 3. Considering that no glass transition is observed in Fe– magnetic properties, i.e., rather high saturation magnetization Co–Ni–B–Si system, we can notice again the importance of reaching 1.3 T in the Fe-rich composition range above 0.8 the addition of the small amount of Nb as the third element and low coercivity of 1.0 to 2.5 A/m in the wide composition leading to the satisfaction of the three empirical component range of 0.25–1.0Fe and 0–0.6Ni. Thus, the appearance of rules for stabilization of supercooled liquid. As an example, ferromagnetic property at room temperature is dependent on Fig. 4 shows the outer shape and surface appearance of the Ni and Fe contents. The decrease of coercivity with cast Fe–Co-based glassy alloy rods with diameters up to increasing Co content has been recognized to originate from 5 mm. These alloy rods have smooth outer surface and shiny the reduction of saturation magnetostriction.26) metallic luster and no crystalline peaks are recognized even Figure 7 shows the relationship between coercivity and for the 5 mm rod. electrical resistivity for Fe-based bulk glassy alloys in Fe–B– Figure 5 shows the compositional dependence of com- Si–Nb and Fe–Ga–P–C–B base systems, together with the pressive fracture strength of the cast Fe–Co–Ni–B–Si–Nb data of amorphous and nanocrystalline alloys which require alloy rods. The high strength of over 4000 MPa is obtained in high cooling rates of over 105 K/s for preparation as well as the wide composition range of 0–1.0Co and 0–0.7Ni and the Co43Fe20Ta5:5B31:5 bulk glassy alloy. It is characterized that Developments and Applications of Bulk Glassy Alloys in Late Transition Metal Base System 1279
Fe-based Co43Fe20Ta5.5B31.5 b
Fig. 7 Relationship between coercivity and electrical resistivity for Fe- and Co-based bulk glassy alloys. The data of conventional amorphous and nanocrystalline alloys are also shown for comparison.
∆V: Volume of "defects" (Initial stress) Fig. 9 Compressive true stress-true strain curves of Co43Fe20Ta5:5B31:5 λ ρ : Density of "defects" glassy alloy rod deformed at various temperatures between room temper- Coercivity HV∝ ∆ ρ s d cdλ : Saturated magnetostriction ature and 873 K. Js s
Js: Saturated magnetization
G1 Fe P B Si G1 Fe80P12B4Si4 1.0 G2 Fe76Al4P12B4Si4
G3 Fe73Al5Ga2P11C5B4
G4 Fe72Al5Ga2P11.55C5.2B4.2 G5 Fe Al Ga P C B G5 Fe73Al2.86Ga1.14P12.65C5.75B4.6 0.5 (a) 25 oC (b) 25 oC G6 Fe77Al2.14Ga0.84P8.4C5B4Si2.6
G7 Fe78Al2P10B6Ge4
G8 Fe75Al5P10B6Ge4 s (e) G9 Fe73Al5Ga2P10B6Ge4 0.0
G14 G10 [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 G12 G13 G11 [(Fe Co ) B Si ] Nb o o
0.6 0.4 0.75 0.2 0.05 96 4 M/M G11 0.6 0.4 0.75 0.2 0.05 96 4 (c) 100 C (d) 200 C Deposition temperature G10 G12 [(Fe Co ) B Si ] Nb 0.7 0.3 0.75 0.2 0.05 96 4 o G13 [(Fe0.8Co0.2)0.75B0.2Si0.05]96Nb4 -0.5 25 C G14 [(Fe Co ) B Si ] Nb o G14 [(Fe0.9Co0.1)0.75B0.2Si0.05]96Nb4 100 C F1 Fe80B20 o F2 Fe B Si F2 Fe78B13Si9 -1.0 200 C F3 Fe80B13C7 F4 Fe P C B F4 Fe80P16C3B1 -80 -60 -40 -20 0 20 40 60 80 Fig. 8 Relationship between coercivity and the ratio of saturation Magnetic Field, H /Oe magnetostriction to saturation magnetization for Fe-based bulk glassy alloys. The data of amorphous type alloys are also shown for comparison. Fig. 10 Spin reorientation from perpendicular to in-plane in Co–Fe–Ta–B thin films with increasing deposition temperature. Hysteretic loops at 300 K for Co–Fe–Ta–B thin films deposited at different Ts. Insets—shows the Fe- and Co-based glassy alloys have better combination the MFM images (area 20 mm 20 mm) for (a) film deposited at 25 C— of lower coercivity and higher electrical resistivity among all Virgin state (b) at 25 C—in remanence state (c) at 100 C—in remanence soft magnetic metallic alloys. The lower coercivity is state, (d) at 200 C—in remanence state, and (e) typical topography of Co– Fe–Ta–B thin films. presumably due to the smaller magnetic anisotropy and lower internal stress. We examined in more details the contribution of internal stress to coercivity. It has previously We have reported that Co–Fe–Ta–B base bulk glassy been reported that the coercivity is proportional to the ratio of alloys exhibit a large supercooled liquid region above 70 K saturation magnetostrictionffiffiffiffiffi ( s) to saturation magnetization before crystallization and the stabilization of the supercooled p 27) (Js), i.e.,Hcv V d ð s=JsÞ, and hence the slope is liquid enables the formation of bulk glassy alloy rods with related to the volume and density of internal defects diameters up to at least 2 mm.15) It has subsequently been considering mainly of free volumes in the glassy structure. reported that the Co–Fe–Ta–B base bulk glassy alloy rods Figure 8 shows good linear relations between Hc and the exhibit very high yield strength of about 5200 MPa at room ratio of s to Js for Fe-based glassy and amorphous alloys. It temperature as well as high elevated temperature strength of is also noticed that their slopes are clearly distinguished over 2000 MPa in the wide temperature range up to 585 C, as between the glassy type alloys and the amorphous type alloys shown in Fig. 9.15) In addition to the high strength, the Co- and the slope is much smaller for the glassy type alloys. This based glassy alloy in a ring shape form of 1 mm in thickness, difference indicates that the structure of the glassy alloys is 10 mm in outer diameter and 5 mm in inner diameter exhibits distinguished from that of amorphous type alloys and excellent soft magnetic properties, i.e., extremely high includes much lower volume and density of internal defects. maximum permeability reaching 500000 and very low The formation of the more homogenized disordered atomic coercivity of 0.26 A/m. configurations is concluded to be the origin for the lower Considering that the extremely soft magnetic properties coercivity for the glassy type alloys as compared with the originate from highly homogeneous magnetic domain struc- amorphous type alloys including crystalline nuclei and ture in the cast alloy ring, we tried to fabricate a soft magnetic density fluctuations. glassy thin film exhibiting unique soft magnetic properties 1280 A. Inoue, B. Shen and A. Takeuchi
tension compression compression
strain rate strain rate strain rate = 5× 10-4 = 8.3 × 10-4 = 4.8× 10-4
(1) Ni53Nib20Ti10Zr8Co6Cu3 (2) Ni50Pd30P20
Fig. 11 Stress-strain curves of Ni-based bulk glassy alloys belonging to metal-metal and metal-metalloid types under tensile and compressive deformation modes.
101 101
0 SUS316L 0 10 10 SUS316L -2 -2 x=5 x=5 x=0 x=0 -1 -1 / A m / A m
I 10
I 10
10-2 10-2 x=15 x=25 x=15 x=25 Ni Nb Ta Ti Current Density, Current Density, -3 60 25-x x 15 Current Density, -3 Ni Nb Ta Ti 10 melt-spun ribbon 10 60 25-x x 15 353 K, open to air melt-spun ribbon in pH 2 H SO 353 K, open to air 2 4 in pH 2 H SO +500 ppm NaCl 2 4 10-4 10-4 0.0 0.5 1.0 1.5 0.0 0.5 1.0 1.5 Potential, E / V vs Ag/AgCl Potential, E / V vs Ag/AgCl
Fig. 12 Anodic polarization curves of Ni60Nb25 xTaxTi15 glassy alloys.
through the control of the structure-sensitive magnetic mixture of -Fe, Fe2B, Fe3B and Fe3Si equilibrium phases domain by a sputtering technique. The Co–Fe–Ta–B glassy for Fe-based amorphous type alloys which require high alloy film with a thickness of 2.6 mm deposited at 298 K had a cooling rates for amorphous phase formation.30) fine perpendicular type domain structure with a spacing of about 1700 nm and the domain structure changes to an in- 4. Ni- and Cu-based Bulk Glassy Alloys plane type for the film deposited at 473 K, accompanying the significant change in the magnetic properties, as shown in Following the Fe- and Co-based bulk glassy alloys, we Fig. 10.28) The success of synthesizing the glassy alloy thin introduce recent progress in Ni- and Cu-based bulk glassy film having the fine perpendicular type domain structure even alloys developed in our group. Figure 11 shows stress-strain at a large thickness of 2.6 mm is promising for future curves of Ni-based bulk glassy alloys in tensile and development as a new type of perpendicular type information compressive deformation modes. The tensile fracture recording material because the previous magnetic thin film strength is as high as 2700 MPa for the metal-metal type thickness with the perpendicular domain structure is limited alloy,18) while the metal-metalloid type alloy exhibits rather to less than several hundreds nm.29) high compressive fracture strength of 1800 MPa as well as We have previously reported that the Fe- and Co-based large compressive plastic strain of 7.5%.31) The high tensile bulk glassy alloys belonging to the metal-metalloid type have strength of the Ni-based metal-metal type alloy is believed to a unique network-like atomic configuration in which dis- be the highest for all the bulk glassy alloys, though much torted trigonal prisms of Fe or Co and B are connected with higher strength has been obtained under a compressive each other in edge- and face-shared configuration modes deformation mode. It is therefore concluded that the metal- through glue atoms of Ln, Zr, Hf, Nb or Ta.5,6) This network- metal type Ni-based bulk glassy alloys are appropriate for like short-range ordered atomic configuration can suppress structural materials which require simultaneously high effectively the long-range rearrangement of the constituent strength and high ductility. elements which is necessary for the progress of crystalliza- The Ni-based bulk glassy alloys containing Nb or Ta as tion, leading to the stabilization of supercooled liquid. solute element exhibit high corrosion resistance in extremely Reflecting the formation of the network-like short-range severe circumferential condition which is required for fuel ordered atomic configuration, all the Fe- and Co-based bulk cell applications, i.e., in pH2 H2SO4 at 353 K and in pH2 glassy alloys in metal-metalloid alloy system have a unique H2SO4 containing 500 ppm NaCl or NaF at 353 K. As primary crystallization phase of complex fcc (Fe,Co)23B6 exemplified in Fig. 12, the addition of Ta causes the increase having a large lattice parameter of about 1.2 nm and in anodic potential and the decrease in corrosive current including 96 atoms in a unit volume.13,15) This phase is density, resulting in a much better corrosion resistance as different from the primary crystalline phase consisting of the compared with SUS316L. Developments and Applications of Bulk Glassy Alloys in Late Transition Metal Base System 1281 / MPa
σ
/ MPa σ
× -2
Tensile Stress, strain rate = 2.4 10 Compressive Stress,
ε (%)
Fig. 13 Stress-strain curves of Cu-based bulk glassy alloys under tensile and compressive deformation modes. ) B σ Bulk 5) Zr41.2Ti13.8Cu12.5Ni10Be22.5(S,4B,R=0.1) 1 6) Pd40Cu30Ni10P20(S,RB,R= –1) 7) Zr55Al10Cu30Ni5(S,AX,R=0.5) 2) Zr Cu Al Pd (N,RB,R= –1)2) Zr–Pd3 BGA 50 37 10 3 S single phase Zr Al Cu Ni (N,AX,R=0.1)1) N nanocrystal 4) 55 10 30 5 3) Cu60Zr30Ti10(N,AX,R=0.1) Ti BGA 4) 6) Ti41.5Zr2.5Hf5Cu42.5Ni7.5Si1(N,AX,R=0.1) Pd BGA Ribbon 8) 3) Co75Si10B15(AX,R=0) Cu BGA Pd Si (AX,R=0)9) 80 20 10)
) / Tensile Stress ( Tensile ) / Pd Cu Si (AX,R=0–0.62) 77.5 6 16.5 10) a 0.2 Ni49Fe29P14B6Si2(AX,R=0–0.71) σ 1) 8) Ni75Si8B17(AX,R=0) Zr BGA Ni Si B (AX,R=0.1)11) AX axial loading 78 10 12 12) 4B 4 points bending Fe92B3Si5(AX,R=0) Fe Si B (AX,R=0.2)13) RB rotating bending 0.1 75 10 15 13) R stress ratio Fe75Si10B15(AX,R=0.6)
Zr–Be BGA5) 0.02 102 104 106 108 Applied Amplitude Stress (
Number of Cycles, Nf / cycle
Fig. 14 S–N curves normalized by the tensile strength ( B) for bulk glassy alloys and amorphous alloy ribbons.
Figure 13 shows tensile and compressive stress-strain being comparable to that for SCM435 steel and much higher curves of Cu-based bulk glassy alloys in Cu–Zr–Ti and Cu– than those for Ti-based crystalline alloys and Zr-based bulk Hf–Ti systems.20) The Cu-based alloy rods exhibit high glassy alloys.35) The fatigue crack initiated at the defect site tensile strength of 2000 to 2100 MPa and have plastic strains which was located on the outer surface of the rod specimen of about 1.5% under a compressive deformation mode. It has and propagated into the inner region, accompanying distinct previously been reported that the tensile fracture strength of striation patterns. The final fatigue fracture region consisted the Cu–Zr–Ti alloy increases further to about 2500 MPa for of a well-developed vein pattern. Although the fatigue the more multi-component Cu-based alloys caused by the strength of the Cu–Zr–Ti glassy alloy is relatively high, it is addition of Be or Y.21,23) A very large supercooled liquid expected that the elimination of surface defects caused by the region with the temperature interval above 100 K is also decreases of inclusions and casting-introduced pores results obtained for the Cu–Hf–Al base alloys containing 5 at %Ag in further improvement of fatigue strength. The fracture 24) or Pd and the largest Tx reaches as large as 110 K which toughness of the Cu–Zr–Ti bulk glassy alloy sheets was also is the largest value for all late transition metal base bulk evaluated by using the test specimen including fatigue pre- glassy alloys. crack which satisfies the ASTM E399 criterion36) for the size We further measured fatigue strength of the Cu–Zr–Hf and dimension. The fracture toughness was measured to be bulk glassy alloy rod with high tensile strength of 2000 MPa about 68 MPam1=2 which was slightly higher than that (40– under a uniaxial tension-tension applied load. The fatigue 60 MPam1=2) for Zr-based bulk glassy alloys.37) It is thus endurance limit defined by the ratio of applied tensile noticed that the Cu–Zr–Ti bulk gassy alloy exhibits high amplitude stress ( a) to tensile fracture strength ( B) after the tensile strength, high ductility, high fatigue strength and high cycles of 107 is 0.24 for the Cu-based alloy, as shown in fracture toughness and all these mechanical properties are Fig. 14.32) The fatigue limit is much higher than 0.14 for Zr– superior to those for Zr-based bulk glassy alloys. Al–Ni–Cu bulk glassy alloy33) and 0.02 for Zr–Ti–Be–Ni–Cu By adding Ta element, which is immiscible to Cu, to 34) bulk glassy alloy. The Cu–Ti–Zr bulk glassy alloy also has Cu60Hf25Ti15 alloy, we can obtain a mixed phase alloy a high tensile stress amplitude of 480 MPa after 107 cycles,32) consisting of homogeneously dispersed bcc-Ta rich dendrite 1282 A. Inoue, B. Shen and A. Takeuchi phase with a size of about 15 mm embedded in a glassy matrix.38) When the volume fraction of the bcc-Ta phase was about 11%, the dendrite-dispersed Cu-based alloy exhibited high yield strength of 2100 MPa and large plastic strain of 34% which was much larger than that (1.6%) for the glassy single phase alloy. We can observe a high density of shear bands on the outer surface and the fracture occurs along the maximum shear stress plane. The significant increase in compressive plasticity is presumably due to easy generation of shear bands at the glass/dendrite interface through the increase in the stress concentration at the interface caused by the difference in the mechanical strength between the two phases.
5. Pd- and Pt-based Bulk Glassy Alloys
For the Pd- and Pt-based bulk glassy alloys, we developed a Pd–Cu–Ni–P bulk glassy alloy with an extremely low critical cooling rate of the order 0.01 K/s in 1996.39) Very recently, we also succeeded in finding another type of bulk Fig. 15 Relationship between tensile or compressive fracture strength and Young’s modulus for late transition metal base bulk glassy alloys. The glassy alloys with extremely high GFA in Pd–Pt–Cu–P alloy data of conventional crystalline alloys are also shown for comparison. system without Ni.40) The critical cooling rate was lower than 1 K/s and the maximum sample thickness was larger than 50 mm. This is concluded to be the second alloy system in the strength is dominated by the bonding nature among the which bulk glassy alloys have large critical sizes above constituent elements. 50 mm and low critical cooling rates below 1 K/s. As shown in Fig. 16, we also scarcely recognized the correlation between the critical sample diameter (Dmax) and 6. Correlations Among Fundamental Properties of Late the reduced glass transition temperature (Tg=Tl) or the Transition Metal Base Bulk Glassy Alloys supercooled liquid region ( Tx) for the late transition metal base bulk glassy alloys, though there are significant scatter- Figure 15 summarizes the relationship between tensile or ings. The correlation suggests that the high glass-forming compressive fracture strength and Young’s modulus for the ability is due to the combination of these two factors, i.e., late transition metal base bulk glassy alloys, together with the steep increase in viscosity of supercooled liquid with data of conventional crystalline alloys. One can see a good decreasing temperature and high resistance of supercooled linear relation. The strength and Young’s modulus increase in liquid against crystallization. the order of Pt-, Pd-, Cu-, Ni-, Fe- and Co-based alloys. The strength value at the same Young’s modulus is about three 7. Applications times higher than that for crystalline alloys. The slope of the linear relation corresponding to elastic strain limit is 2% Table 5 summarizes the features of fundamental properties which is about three times larger than that (0.65%) for of the late transition metal base bulk glassy alloys. Typical crystalline alloys. Also, the deformation and fracture behav- fundamental properties of Fe-, Co-, Ni- and Cu-based bulk iors of the bulk glassy alloys are independent of alloy glassy alloys were demonstrated in previous sections. In component and strength level. The similar linear relation is addition, it is important to point out that the Pt–Pd–Cu–P also recognized between fracture strength and Tg or Tl for the bulk glassy alloys have very useful combination of low Tg of late transition metal base bulk glassy alloys, indicating that about 500 K, a large supercooled liquid region of over 90 K
Fig. 16 Relationship between critical diameter and reduced glass-transition temperature or supercooled liquid region for late transition metal base bulk glassy alloys. Developments and Applications of Bulk Glassy Alloys in Late Transition Metal Base System 1283
Table 5 Features of fundamental properties for late transition metal base has used at least ten kinds of pressure sensors such as bulk glassy alloys. injection control, oil pressure control, air conditioning, Fe-based 1. Soft Magnetism (Glass, Nano-crystal) clogging monitor, brake control and so on. If the fuel cell 2. Hard Magnetism (Nano-crystal) system will be employed, the total number of the pressure 3. High Corrosion Resistance sensors is expected to increase about twice, indicating the 4. High Endurance against Cycled Impact Deformation possibility of the significant increase of pressure sensor Co-based 1. Soft Magnetism market for automobiles in the near future. 2. High Strength Micro-geared motors with high torque have been used in 3. High Corrosion Resistance various engineering fields. The minimum size of the motors was 12 mm in 1980 and decreased to 7 mm in 2000 and Ni-based 1. High Strength, High Ductility 2.4 mm at present. We tried to fabricate micro-geared motors 2. High Corrosion Resistance having the features of the world smallest size of 1.5 mm, 3. High Hydrogen Permeation heavy loadable and high durability by using the high-strength Cu-based 1. High Strength, High Ductility (Glass, Nano-crystal) Ni-based bulk glassy alloy through the resolution of various 2. High Fracture Toughness, High Fatigue Strength technical difficulties, as shown in Fig. 17.43) The constructing 3. High Corrosion Resistance parts of the 1.5 mm diameter geared motor cannot be made by Pd-based 1. High Strength any mechanical machining techniques, though the 2.4 mm 2. High Fatigue Strength, Rather High Fracture Toughness diameter geared motor can be scarcely constructed by 3. High Corrosion Resistance mechanically machined SK-4 steel parts. It is noticed that Pt-based 1. Very Low Tg the durability of Ni-based glassy alloy gears in the 2.4 mm 2. Very Low TL diameter geared motor increased by 313 times as compared 3. High GFA with the SK-4 steel gears. Even after the rotation number of 4. High Corrosion Resistance 1875 million, the Ni-based glassy alloy gear keeps the 5. Good Nano-imprintability original shape, being in good contrast to the significant wear loss of the steel gear after 6 million rotation numbers. Besides, we succeeded in making the 1.5 mm micro-geared and high corrosion resistance which are suitable for viscous motor using Ni-based glassy alloy gear parts such as shaft flow working treatments on a nanometer scale in the with carrier, planetary gear and carrier with sun-gear. It was supercooled liquid region. By the combination of these confirmed that the micro-geared motor had high-rotating unique features, the late transition metal base bulk glassy torques of 0.1 mNm at 2 stages stacked gear-ratio reduction alloys have already gained various application fields. Their system and 0.6 mNm at 3 stages which were 6 to 20 times application examples will be briefly explained in this section. higher than the vibration force for conventional geared motor We developed a mass-production type water atomization with a diameter of 4.5 mm in mobile telephones. These technique which enabled the production of Fe-based glassy micro-geared motors are expected to be used in advanced alloy powders with sizes ranging from 0.1 to 2 mm and its medical equipments such as endoscope, micro-pump, rota- production ability reached 20 tons per month. These Fe-based blator and catheter for thrombus removal, precision optics, glassy alloy balls have been commercialized as shot peening micro-industries, micro-factory and so on. balls.41) It has been demonstrated that the shot penning effect Fe-based soft magnetic glassy alloys in Fe–Co–Ga-metal- leading to the generation of compressive residual stress field loid and Fe–Co–B–Si–Nb systems have been commercial- on the surface of material is much superior to that for ized as consolidated magnetic cores for power supplies such conventional crystalline shot penning balls, in addition to the as choke coils, common mode and noise filter.5,6) The really much longer endurance time for the Fe-based glassy alloy commercialized magnetic cores exhibit very good soft balls. magnetic properties, i.e., nearly constant relative permeabil- In comparison with SUS630 which has been used as ity in a wide frequency range up to several MHz, good linear conventional pressure sensor, the Ni–Nb–Ti–Zr–Cu–Co bulk relationship between permeability and DC bias field, and glassy alloy has much higher tensile strength, much lower much lower core losses as compared with Sendust and Young’s modulus and much better corrosion resistance. By Permalloy. These Fe-based glassy alloys in Fe–Co–Ga–P–C– use of these features, the Ni-based bulk glassy alloy is B–Si and Fe–Co–B–Si–Nb systems with very high effective expected to be applied to a new type of pressure sensor permeability above 100000 at 1 kHz and rather high Js of 1.2 exhibiting higher pressure capability and higher sensitivi- to 1.3 T in a thick sheet form have been tested as the yoke ty.42) We produced Ni-based glassy alloy diaphragms by the material in precision positioning linear actuators in which the die casting process and made the strain gauge pattern on the wiring pitch for circuit process unit can be controlled on a surface of the diaphragms by the low temperature chemical scale of 10 to 30 nm. The linear actuator using Fe-based vapor deposition technique. It has been confirmed that the glassy alloy yoke sheets exhibits higher Lorentz force of pressure sensors made of Ni- and Zr-based bulk glassy alloys 0.35 N in a frequency range of 20 to 40 Hz as compared with have much higher sensitivity than that for SUS630. The use those for other soft magnetic alloys, indicating that the linear of the much higher sensitivity characteristics also has lead to actuator is appropriate for small, large force, fast drive and the miniaturization of the pressure sensor from 8.5 mm in energy-saving types. diameter for the conventional standard sensor to 5.0 mm for By the recent rapid development of nano- and micro-scale the Ni-based glassy alloy sensor. At present, one automobile working process techniques using ion beam, electron beam 1284 A. Inoue, B. Shen and A. Takeuchi
Fig. 17 Micro-geared motor with the world smallest size of 1.5 mm in diameter constructed by Ni-based glassy alloy geared parts and illustration of its construction diagram.
Fig. 18 Periodically nanostructured surfaces fabricated by superplastic nano-forging of Pt-based bulk glassy alloys with focus ion beam machined dies of Zr-based metallic glass.
45) and LIGA process etc., the importance of materials with Fig. 18. The Pt48:75Pd9:75Cu19:5P22 bulk glassy alloy with homogeneous structure on a nanometer scale has signifi- low Tg of 502 K and large Tx of 85 K can be regarded as an cantly increased. In the case of metallic alloys, the alloys ideal viscous flow working material on a nanometer scale. with such features are limited to glassy and nanocrystalline The low Tg enabled the use of polyimide die supported with alloys. The glassy alloys have much homogeneous structure copper plate and only one cycle viscous flow pressing against and can be deformed via viscous flow working even at much the polyimide die in the supercooled liquid region produced lower temperatures as compared with nanocrystalline alloys. complex micro-inductors. We have confirmed that the By applying the focused ion beam (FIB) technique to bulk minimum pattern size caused by the viscous flow die forging glassy alloys, we have fabricated various complex patterns process reaches as small as 22 nm, as is evidenced from the with smooth surface on a nanometer scale which cannot be fabrication of the imprinted nano-data-pit patterns for next obtained for conventional crystalline alloys.44) The control- generation DVD recording storage material in Fig. 19. lable minimum size of the complex pattern by the FIB technique reached as small as 12 nm. We fabricated bulk 8. Conclusions glassy alloy surfaces having highly functional characteristics through the FIB working of Pt-based bulk glassy alloys to The development of advanced metallic materials by use of nanometer-scale controlled functional surface, as shown in the science and technology of supercooled metallic liquid has Developments and Applications of Bulk Glassy Alloys in Late Transition Metal Base System 1285
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