Titanium Is Widely Distributed Throughout the Universe. It Has Been

1960s has served to somewhat offset the in each ofthe alloys Ti-6Al-2Sn-4Zr-2Mo decline in military demand during the (i.e., "Ti-6242"), Ti-6Al-2Sn-4Zr-6Mo (i.e., same period, thereby yielding not only a "Ti-6246"), and Ti-11.5Mo-6Zr-4.5Sn (i.e., Titanium is widely distributed netgrowth but a relatively steady one. "~-III") was on the increase. Today the al throughout the universe. It has been dis Titanium (meaning titanium and its loy Ti-6242 to which about 0.1% Si has covered in the stars, in interstellar dust, alloys) has two principal virtues: (1) a been addedis beingusedintitanium alloy in meteorites, and on the surface of the high strength/weight ratio and (2) good forgings andhas received extensive study earth. Its concentration withinthe earth's corrosion resistance. At one time or an and use in its role as a gas-turbine com crust of about 0.60/0 makes it the fourth other practically all aerospace structures pressor-disc material. Finallyit shouldbe most abundant of the structural metals -airframes, skin, and engine compo noted that Ti-10V-2Fe-3Al has been the (after aluminum, iron, and magnesium). nents-have benefited from the introduc beneficiary ofthe renewed interest being It is 20 times more prevalent than chro tion of titanium. Nonaerospace applica shown in so-called "near-~" titanium al a mium, 30 times more than nickel, 60 tions include steam-turbine blades, loys [DUE80 ] [l'ER80] [TOR80], while it is times more than copper, 100 times more hydrogen-storage media, high-current! atlast becomingrecognizedthat Ti-5ONb, than tungsten, and 600 times more than high-field superconductors, condenser one ofthe most important oftoday's tech molybdenum. This abundance is to some tubing for nuclear and fossil-fuel power nical superconductors, is in fact a ~-Ti al extent illusory, however, in that titanium generation, and other corrosion-resistant loy [CoL81]. is not so frequently found in economically applications such as components for extractable concentrations. Concentrated ocean thennal-energy conversion, off sources of the metal are the minerals il shore oil drilling, marine-submersible menite, titanomagnetite, rutile, anatase, vessels, desalination plants, waste-treat In order to cope with unexpected in and brookite. ment plants, the pulp-and-paper indus creases in the demand for a metal, it is Ilmenite is haematite (Fe203) in try, and the chemical and petrochemical helpful to be able to rely on a copious and whichhalfoftheironhasbeenreplacedby industries. stable supply of the basic ore. The tita titanium; titanomagnetite is magnetite Interest in the properties of titanium nium industry is fortunate in this regard. (Fe304) in which one-third ofthe iron has and its alloys began to accelerate in the Titanium dioxide is produced in large been replaced by titanium. Rutile is Ti02 late 1940s [CRA49] and early 1950s as quantities for many applications, so much (as are anatase and brookite). Naturally their potential as high-temperature, so that in 1977, for example, only a few occurring (and titanium-deficient) il high-strength/weight materials with percent of the world's production of tita menite consists ofhaematiteparticlesin a aeronautical applications became more nium ore was tapped for metallic sponge matrix of ilmenite; naturally occurring and more widely recognized. The history refinement (most of the mined ore being (and, again, titanium-deficient) ti oftitanium andits developmentinalloyed used to make paint pigment). Thus, since tanomagnetite is magnetite containing form has beendescribedin detailinthein the overall demandfor rawmaterialis not lathsofilmenite. Inshort, themostimpor troduction to the first International Con subjectto the same fluctuations as the de tant titanium minerals are ilmenite and ference on the subject [JAF70] and in the mand for the metal, should the latter un rutile. introduction to ZWICKER's comprehensive dergo a significant increase at any time, Titanium was first discovered in min metallurgical treatise Titan und TItanle there is at least a strong raw-material erals now knovvn as rutile by W Gregor gierungen [ZWI74]. As evidenced by the base from which to draw. (England) and M.H. Klaproth (Gennany) papers presentedatthe subsequentInter Industry's growing awareness of the in about 1790. The first commercial mill national Conferences, titanium andits al need for energy conservation has served products were produced by the Titanium loys have by now found widespread use in to emphasize an unfortunate charac Metals Company of America (TMCA) the aerospace industry (for both frame teristic of the current methods of tita around 1950. From that time to the pres andengine components) andinthe chemi nium metal refinement: their energy in ent, production ofthe metal has grown at cal and related industries, where advan tensiveness. The energy required to an average annual rate of about 8%. Su tage can be taken oftheir corrosion resis produce a ton ofsponge-titanium from its perimposed upon part of this temporal tance. According to WOOD [Woo72], by are is 16 times that needed to produce a growth curve is a largefluctuating compo 1972 about 30 commercial alloys were al ton of steel, 3.7 times that needed for fer nent, a reminder ofthe capriciousness of ready on the marketinmill-product form. rochrome, 1.7 times that needed for alu the materials demands of the aerospace Ofthese, the eight most favored composi minum production, and a little more than industry, titanium's principalmarket dur tions, accounting for some 900/0 of the that needed for a I-ton ingot of magne ingthe early years. Fortunatelyfor the ti sales, were three grades ofunalloyedtita sium. Since, however, the heats offorma tanium-production industry, the 13% an nium and the alloys Ti-5Al-2.5Sn, Ti-6Al tion ofrutile (- -228 kcallmol), haematite nual growth rate exhibited by the civilian 4~ Ti-8Al-1Mo-1~ Ti-6Al-6V-2Sn, andTi (- -200 kcallmol), and magnetite (- -268 sector ofthe total market since the early 13V-11Cr-3Al. At that time also, interest kcall mol) are in the ratio of 1:0.88:1.18, Copyright © 1994 ASM International ® All rights reserved. Materials Properties Handbook: Titanium Alloys, 06005G www.asminternational.org 4/I1Jn'''~II'~1 ME~talllur·~v of Titanium

Table 1.1 Total Impurity Contents of Io Table 1.2 Typical Interstitial Impurity Contents of Several Grades of Titanium dide- and Kroll-Process Titaniums (in wt%) [RAS72] Interstitial content, ppm Data Grade oftitanium N source Element IodideTi Kroll Ti MRC (MARZ-grade) 78 6 63 1 Mg 0.01 0.13 MRC (VP-grade) 150 40 350 2 Si 0.01 0.05 TMC electrorefined sponge (grade ELXX) 40 370 3 AI 0.02 Kroll-process (Toho sponge) 110 860 4 Fe 0.01 0.20 Kroll-process 800 400 1100 5 Ni 0.01 Iodide-process 100 200 200 5 Co 0.02 Cr 0.01 (1) Materials Research Corp.: Zone-refined; supplied typical analysis. (2) Materials Research Corp.: Vacuum Mn 0.005 0.02 melted; supplied typical analysis. (3) Titanium Metals Corp.: See also rCoL701. (4) See rCoL701. (5) See Table 1.1. C 0.01 0.08 N 0.02 0.04 0 0.02 0.11

there seems to be some scope for increas ucts are commercially pure sponge-tita wire, which acts as nucleus for the growth ing the energy efficiency ofthe titanium nium (in the fonn ofa porous, gray, coke ofa long cylindrical bar ofhigh-purity ti refinement process. like mass) and MgC12' most ofwhich can tanium crystals. Typical impurity con The most well-known method oftita be drained out ofthe reaction chamber as tents of several grades of titanium are a liquid. The MgC1 is electrolytically nium production is the Kroll process, 2 listedin Tables 1.1 and 1.2. recycled. The titanium sponge is conso which involves the reduction of TiC1 by 4 lidated by arc melting in a water-cooled These and other standard commer magnesium. The first step in the process copper crucible: this process involves cial methods oftitanium production, such is the preparation ofthe tetrachloride it several iterations ofa procedure in which as the sodium-reduction (or Hunter) proc self, which is carried out by the chlorina an arc is maintained between a consu tionofa mixture ofcarbonwithrutileoril ess, the direct-oxide-reduction process, mable compacted-sponge-titanium elec andthe electrolytic process, have been de menite. The Kroll magnesium-reduction trode and a pool ofmolten sponge. scribed in detail by MCQUILIA'I [McQ56, reaction takes place in a closed heated re The highest purity titanium is pre Chap. 2], HOCH [HoC73b], and ZWICKER actor vessel under an inert atmosphere. pared for research purposes by the iodide Liquid TiC14 is introduced to the liquid process. Crude titanium is first reacted [ZWI74, pp. 21-27J, while some new ap magnesium already presentinthe vessel, withiodinein aninert atmosphere toform proaches developed in the Soviet Union thereby initiating the reaction 2Mg + titanium iodide. This can then be decom have been outlined by REzNICHENKO and TiCl4 -7 2MgC12 + Ti. The reaction prod- posed at the surface ofa heated titanium coworkers [REz82, REz82aJ.