GB1134492A - Methods of improving the mechanical properties of metals and their alloys - Google Patents

Abstract

1,134,492. Improving physical properties. JOHNSON, MATTHEY & CO; Ltd. 3 June, 1965 [11 March, 1964; 20 March, 1964; 17 April, 1964], Nos. 10239/64, 11886/64 and 15973/64. Heading B3V. [Also in Divisions B1 and C7] A metal or alloy which has been strengthened by the incorporation of a dispersed non-metallic phase such as an oxide, carbide, boride, silicide or nitride has its mechanical properties further improved by cold-working and subsequent annealing, the amount of cold-working being such that the recrystallization results in a structure of elongated grains which are orientated in the direction of working. The degree of orientation may be such that at least 50% of the grains have their major axes lying within 30 degrees of the direction of working, while the grains may have a length width ratio greater than 5 and up to 12.5. Preferably the amount of cold-working exceeds 80%. The invention is applicable to both noble and base metals and their alloys, which may have been made by powder-metallurgical methods, but is concerned particularly with the treatment of dispersionstrengthened platinum and its alloys, which may subsequently be used for catalyst gauges, electric furnace windings, resistance thermometers, thermocouples, or bushings, melting crucibles or stimers used in the manufacture of glass. Particular materials exemplified are sintered platinum/0.04% titanium carbide, platinum/0À5% thorium, and 10% platinum/ 90% thorium/0-04% titanium carbide, which were cold worked by about 95% and subsequently annealed at 1400‹ C. Base metal compositions are exemplified by copper containing 0.04% of titanium carbide, which was coldreduced by about 80% and then annealed at 350‹ C. The precious metal base compositions are sintered at 1400‹ C. for 1-3 hours, possibly after the powders have been sinterered at 800‹ C. prior to pressing at 8-10 tons/sq. inch. Some specimens were re-pressed to 80% of theoretical density and re-sintered for 2 hours at 1400‹C. Compositions containing thorium nitrate were produced by mixing platinum powder with an aqueous solution of thorium nitrate, dried at 100‹ C., and heated for 3 hours at 800‹ C. in hydrogen, while to prepare the copper-base composition copper powder was reduced in hydrogen at 350-400‹ C. for 4 hours, mixed with titanium carbide, dry-milled in a polypropylene mill, annealed at 450‹ C. in vacuum for 2 hours, pressed at 10 tons/sq. inch and sintered in vacuum for 4 hours at 900-950‹ C.