Method for the optimization of the microstructural properties of alpha, beta - titanium alloys, with a simultaneous improvement of the mechanical properties and the toughness

摘要

The invention is a process for simultaneously improving at least two mechanical properties of mill-processed (α + β) titanium alloy, which may or may not contain silicon, which includes steps of heat treating the mill-procesed titanium alloy such that the (α + β) microstructure of said alloy is transformed into an (α + α₂ + β) microstructure, preferably containing no silicides. The heat treating steps involve subjecting the mill-processed titanium alloy to a sequence of thermomechanical process steps, and the mechanical properties which are simultaneously improved include (a) tensile strength at room, cryogenic, and elevated temperatures; (b) fracture toughness; (c) creep resistance; (d) elastic stiffness; (e) thermal stability; (f) hydrogen embrittlement resistance; (g) fatigue; and (h) cryogenic temperature embrittlement resistance. As a consequence of the process, the (α + α₂ + β) microstructure contains equiaxed alpha phase strengthened with α₂ precipitates coexisting with lamellar alpha-beta phase, where the α₂ precipitates are confined totally to the equiaxed primary alpha phase. The invention also encompasses a composition of matter produced by the inventive process, especially one comprising a titanium alloy having an (α + α₂ + β) microstructure.