PRINCIPLES AND PRACTICAL ASPECTS OF TITANIUM HEAT TREATMENT

摘要

In closing, the following points are reiterated in the hope that these few but all-important principles will be understand and applied:n(1) Aluminum and the beta-stabilizing elements confer different properties on titanium. The beta-stabilizing elements make titanium heat treatable and facilitate the fabrication of high-strength alloys. Aluminum raises elevated-temperature strength and makes it possible to hot work at higher temperatures, but reduces workability,n(2) All alpha-beta alloys will respond, in varying degrees, to solution and aging heat treatments. Solution treatments should be carried out at temperatures in the alpha-beta field. Aging temperatures should be at least 800 F and preferably higher to avoid omega embrittlement.n(3) Stress-relief temperatures should be high enough to remove residual stresses induced in forming operations but not high enough to produce appreciable amounts of the beta phase. Beta so produced may be retained upon cooling and, being unstable, may decompose to omega with resultant embrittlement of the alloy. Stress-relief treatments should, in general, not exceed 1150 F.n(4) Until the problem of high-temperature (beta) embrittlement is solved, titanium alloys should not be hot worked at temperatures in excess of the beta transus. If this cannot be avoided, appreciable work must be done at finishing temperatures in the alpha-beta field.