GB815975A - Heat treatment of titanium alloys - Google Patents

Abstract

Titanium-base alloys containing one or more of the alpha promoters Al, Sn, Sb in total amount 0.5-23 per cent, the Al content not exceeding 12 per cent and the Sb content not exceeding 19 per cent, one or more of the eutectoid beta promoters Cu 0.5-20 per cent, Co and Ni 0.5-12 per cent each, Si 0.25-3 per cent, Be 0.1-2 per cent and the remainder Ti at least 50 per cent and impurities are subjected to one of the following heat treatments. Up to one half of the eutectoid beta promoters may be substituted by one or more of Mo, V, Nb, Ta up to 20 per cent in total, Mn up to 5 per cent, Fe up to 3.5 per cent and Cr and W up to 12 per cent in total, the substitution being on a proportionate basis, i.e. where the alloy contains Cu for example in amount of 10 per cent the substituting elements may be present up to the maximum indicated proportions and proportionally lesser amounts of these elements are used with lesser amounts of Cu. The alloys may be annealed by heating above the beta transus temperature until transformation to the beta phase is substantially complete and then cooled at a rate of not over 10 DEG F. per minute to below the eutectoid temperature. The alloy may then be heated at 50 to 100 DEG F. below the eutectoid temperature to remove strains and to promote compound agglomeration after which they are cooled to about room temperature at a rate not less than that of cooling in still air. The alloys may be hardened by heating above the eutectoid temperature until equilibrium of the alloy is substantially complete and then cooling rapidly to below the eutectoid temperature at a rate sufficient to produce a fine eutectoid structure. The alloys may be hardened by heating above the beta transus temperature till transformation to the beta phase is substantially complete or by heating in the alpha-beta range till equilibrium is established and then cooling to below the eutectoid temperature sufficiently rapidly to produce martensite, the cooling rate being at least as rapid as an air cool in still air. The cooled alloy may be aged at a temperature below the eutectoid temperature.