an
1 r/zclMaterials of Conetruetion Review
l e s s Common Metals by E.
M. Sherwood, Battelle Memorial Institute, Columbus, Ohio
Recently developed processing technology is now used to fabricate complex equipment from less common metals on a routine basis
N E W DEVELOPMENTS and immovements in process technology proved to be the key to increased use of the less common metals as materials of construction in the period covered by this review. Some of the newer techniques employed were electrolytic (chemical), erosion (spark), and electron-beam machining, high-energy rate (explosive) forming, radiofrequency and electronbeam welding, plasma-arc cutting, application of protective coatings by chemical vapor deposition and plasma-arc spraying. and further use of the electron-beam technique in melting, zone refining. and metal evaporation. Efforts to prepare metals and alloys of greater chemical purity, using special refining methods considered laboratory curiosities only a few years ago, were rewarded. Exposure of new metals and alloys to environmental conditions simulating the requirements of nuclear engineering and space technology provided valuable property data on which future equipment designs may depend. Evidence of increased activity in the less common metals field was reflected i n a 2076 increase in the published literature dealing with this area of materials technology. I n response to a number of requests, this review now includes beryllium, a less common metal of increasing importance. This review covers the literature which came to the author’s attention in the period June 1960 through May 1961.
Beryllium T h e expanding technology of beryllium was well documented (8, 23> 59). Evidence of its advantages as a material of construction in nuclear engineering was presented (87, 89): and new data regarding its inherent ductility were published (3, 57).
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Metal joining methods found reliable included fusion welding, diffusion welding, braze welding, and furnace brazing (56). Of particular importance is the resistance of beryllium to oxidation a t elevated temperatures (5, 6, 35).
Chromium Emphasis on chromium as a special material of construction declined somewhat. On the other hand, chromium is a promising alloying agent for other less common metals. An electrolytic refining method was described, which shows promise for future application (28) in metal production. Deposition from H 2 C r 0 4 solutions a t high temperature yields metal with a lower tin and oxygen content than that obtained with fluoride electrolytes. General properties of chromium as a material of construction in nuclear reactors were reviewed ( 4 3 ) , and important alloy systems were described ( 4 5 , 46). A new liquid-phase method for the application of chromium coatings on refractory metal bases was described (86). Coatings of chromium 25 to 40 microns in thickness, applied to UOZ fuel particles by chemical vapor dep-
osition, were effective as barrier layers in preventing core-to-cladding reaction in pressure-bonded fuel elements (62).
Hafnium Research activity on hafnium was limited. Important listings of source material containing information regarding hafnium appeared (1, 80).
Molybdenum Molybdenum promises to be of increasing interest as a material of construction in nuclear engineering applications. Properties of significance in this area were summarized (38). Processing of molybdenum using the newer techniques became more commonplace (26). Forming (77), shaping and machining (27, 57, 55, 69, 85):and welding (75, 82-84) all received special attention. New d a t a on the anodic behavior of molybdenum were developed (10). If molybdenum is to be used in nuclear applications, its behavior under various conditions of irradiation must be known. Changes in lattice parameter, micro-
The intensive search for metallic materials o f improved properties for service in extreme environments has led to numerous investigations o f alloy systems among the less common metals. The combined goals of strength at elevated temperatures, ductility at low temperatures, and resistance to corrosion and Oxidation at all femperafures have not yet been achieved, but progress toward them has been significant.
INDUSTRIAL AND ENGINEERING CHEMISTRY
a n v i Materials of Construction Review hardness (34), brittle-fracture stress, load elongation, and yield stress (47) become important. As in the case of chromium, liquid phase coating was investigated as a means of protecting the metal against high-temperature oxidation (67). Molybdenum was evaluated as a plasma-sprayed coating (47). Density, hardness, thermal expansion, and hightemperature tensile properties were determined. New uses for molybdenum in the chemical industry for heat exchangers and for special fasteners are likely (77).
Niobium Renewed interest and expanded research activity involving niobium and its alloys reached a high level, perhaps even exceeding that of 1956, the year during which interest in this metal first reached its peak. Properties significant in nuclear technology were summarized (71). Chemical, physical, and mechanical properties of numerous niobium-based alloy systems were actively explored (7, 19, 39, 40, 53, 70). Niobium responded well to a new high-energy rate forming process, in which a n underwater shock wave, created by a high voltage spark, forces the metal into complex shapes in dies (2). Large niobium forgings (up to 1300 pounds in weight) were produced (73), while thin-walled niobium tubing also became available (74). I t was determined that no measurable changes took place in the oxidation rate of niobium exposed to high neutron fluxes (74). One of the most successful processes yet described for the formation of oxidation resistant coatings on niobium and its alloys involves exposure of the material to zinc vapor in a closed system a t 865" C. (33, 66, 87). T h e influence of alloying elements in such coatings also was established
of importance were summarized in two important reviews (68, 76). New data on the rolling of thin tantalum sheet were presented (37). With progress being made in the development of protective coatings for tantalum, its high-temperature mechanical properties remain important (36). The chemical industry, however, is largely concerned with corrosion problems, many of which can be avoided by substituting tantalum for other materials of construction (73, 22). Further progress in corrosion technology disclosed that hydrogen embrittlement of tantalum in HCl a t 190" C. can be minimized by mechanically attaching or electroplating noble metals on tantalum (77).
Tungsten For some time interest in tungsten has centered on its strength a t elevated temperatures. While this is still one of its most important characteristics, interest in other properties has developed. General publications containing valuable and up-to-date property data appeared during this review period (29, 32). High strength and brittleness a t room temperature render tungsten difficult to fabricate into useful shapes. High velocity forming permits reductions in area of 45 to 1 without the need for cladding or lubricants (52). Further, electron beam processing yields alloy ingots having reduced grain size, better workability, increased shock resistance, and improved ultimate strength (54). The art of joining tungsten has also advanced (58). Tungsten, too, is finding increased use as a protective coating on nuclear fuel particles (60) and for rocket nozzles (65). Residual electrical resistivity can be used as a n index of the damage present in irradiated tungsten (78).
The result of a n extensive investigation of the physical metallurgy of tungsten and its alloys, sponsored by the U. s. Air Force, became available (4). Tungsten single crystal fibers, today a laboratory curiosity, can be used in the fabrication of metallic composite materials of high tensile strength (50). New uses for tungsten in the chemical industry were described (78).
Zirconium Properties and applications of zirconium in nuclear engineering continued to dominate the voluminous published literature in this field. As more nuclear reactors are constructed, the need for this metal increases (25, 88). An important summary of property data for zirconium and its alloys, slanted toward nuclear application, became available (48). T h e method of screening zirconium-bearing materials, scheduled for use in the Naval reactor program, was described (42). Corrosion of zirconium and its alloys in nuclear reactors constituted the most actively studied characteristic of these materials. I n addition to compilations of corrosion data (72), hydrogen pickup during corrosion (9,77), corrosion in polyphenyls (76), mechanism of film growth and breakdown ( Z O ) , influence of irradiation on corrosion ( 2 1 ) , development of corrosion-resistant alloys (24, 79), and factors influencing solution potential (72) were discussed. Various tests, devised to yield data of assistance in design work with commercial Zircaloys, both as fabricated and after irradiation, were carried out (30, 37, 49, 63, 64). A new alloy designation Zircaloy-4 has been added to commercial listings. I t contains 0.15 wt. yo tin, 0.12 wt. % iron, and 0.10 wt. % chromium (63, 64).
(67).
Rhenium Despite its scarcity, rhenium continues to be of interest in materials technology. Its remarkable rate of work hardening, greater than that of any other metal, is believed to be associated with a special network of partial dislocations which develops during cold working ( 75). As an alloying agent with tungsten and molybdenum, it contributes ease of fabricability not achievable with other metals (44).
Tantalum While less abundant than niobium, tantalum possesses superior corrosion resistance in many media. Up-to-date information on this property and others
AVAILABLE FOR
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The complete annotated bibliography of the 1960-61 Materials of Construction Review of Less Common metals by Sherwood.
After one year this material can be obtained from the AD1 Auxiliary Publications Project, Library of Congress, Washington 25, D. C., as Document No. 6846. The price will then be $2.00 for microfilm and $3.75 for photostat copies.
Clip and mail coupon on reverse side VOL. 53, NO. 1 1
NOVEMBER 1961
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literature Cited (1) .4bshire, E., Notestine, S., U. S. Bur. Mines, Inform. Circ. No. 7928, 1960. (2) A m . MachinistlMetalworkzng M f g . 105,
80 (March 6, 1961). (3) Amonenko, V. M., Kruglykh, A. A,, others, Zavodskaya Lab. 26, 625 (May
1960). (4) Atkinson, R. H., U. S. Office Tech. Services, Rept. PB-161978, May 1960, (5) Aylmore, D. W., Gregg, S . J., Jepson, W.B., J . Nuclear Materials 2, 169 (June 1960). (6) Ibid., 3, 190 (February 1961). (7) Bartlett, E. S., Houck, J. A,, Defense Metals Inform. Center Rept. No. 125, Feb. 22, 1960. (8) Beaver, W. W., Lillie, D. W., in “Reactor Handbook,” C. Tipton, ed., Val. 1, Chap. 44, p. 897, Interscience, New York, 1960. (9) Berry, W. E., Vaughan, D. A,, White, E. L., Corrosion 17, 109t (March 1961). (10) Besson, J., Drautzburg, G., Electrochim. Acta 3, 158 (July 1960). (11) Bishop, C. R., Stern. M., J. Metals 13, 144 (February 1961). (12) Bast, W. E., U. S. At. Energy Comm. Rept. TID-3548, March 1960. (13) Brewer, C. W., Chem. Eng. Mining Reu. 52, 58 (July 15, 1960). (14) Cathcart, J. V.: Young, F. CV., Corrosion 17, 77 (February 1961). (15) Churchman, A. T.? Trans. M e t . Soc. A I M E 218, 262 (April 1960). (16) Cochran, F. L., U. S. At. Energy Comm. Rept. NAA-SR-MEMO-4847, 1960. (17) Corrosionomics 5 , No. 2, 2 (1960). (18) Ibid., No. 4, 2 (1960). (19) Corrosion Technol. 8, 7 (January 1961). (20) Cox, B., J . Electrochem. Sot. 108, 24 I1961). ( 2 0 Cdx. B., Alcock, K.. Derrick, F. W., Ibzd.,108, 129 (1961). (22) Cox, F. G., Corrosion Technol. 7, 69 (March 1960). (23) Darwin, G. E., Buddery. J. H., “Metallurgy of the Rarer Metals,” Val. 7, “Beryllium,” Academic Press, New York, 1960. (24) DeMastry, J A., Shober, F. R., Dickerson, R. F.. U. S. At. Energy Comm. Rept. BMI-1418, Feb. 22, 1960. (25) Driear, J. R., Iron Age 185, 107 (Sept. 22, 1960). (26) Droscha. H., Metall 10, 4 (January 1961) . _ I_ ’
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(27) Faust, C. L., Snavely. C. A , Iron Ace 186, 77 (Nov. 3. 1960). (28)Ferrante, M. .I., Good, P. C., others, J . Metals 12, 861 (November 1960).
(29) Fischer, R. B., in “Reactor Handbook,” C. Tipton, ed., Val. 1, Chap. 29, p. 671, Interscience, New York, 1960. (30) Flint, O., Corrosion 16, 99 (May 1960). (31) Ford, H., Alexander, J. M., others, M e t a l Ind. (London) 96, 313 (April 15, 1960). (32) Godfrey, L. E., Bell, P. E., Sterns, H. S., U. S. At. Energy Comm. Rept. LAMS-2401, Vol. 2, p. 209, 1960. (33) Goode, R. J., Pollard, A. J., Meussner, R. A., Rept. NRL Progr. 32, January 1961. (34) Gray, D. L., Cummings, W. V., Jr., Acta M e t . 8,446 (July 1960). (35)7Gregg, S. J., Hussey, R. J., Jepson, Vv, B., J . Nuclear Materials 3, 175 (February 1961). (36) Holden, F. C., Schwartzberg, F. R., Jaffee, R. I., in “Symposium on Newer Materials,” p. 36, ASTM Spec. Tech. Pub. No. 272, 1960. (37) Howe, L. M., Thomas, W. R., J . ~Vuclear Materials 2, 248 (Srptember 1960). (38) Inouye, H., Manly, W. D., in “Reactor Handbook,” C. Tipton, ed., Val. 1, Chap. 25, p. 604, Interscience, New York. 1960. (3q-Jahnkel-L.P., Frank, R. G., Redden, T. K., M e t a l Progr. 77, 69 (June 1960). (40) Ibid.,78, 76 (July 1960). (41) Johnson, A. A,, Phil. Ma,
