Abstract
An investigation has been made of the effects of (a) solution-treatment temperature, (b) cooling rate after solution treatment, (c) aging treatment, and (d) composition (i.e. molybdenum and silicon contents) on the microstructure and mechanical properties of some α-alloys of the Ti–Al–Zr–Mo–Si system related to IMI 685 Ti-alloy composition (Ti–6Al-5Zr–0·5Mo–0·25Si wt-%). β-solution treatment following quenching produces martensitic structures which are accompanied by small amounts of retained β-phase in the molybdenum-containing alloys. Increasing the β-solution treatment temperature does not significantly affect the martensite plate size but increases the original β-grain size, without altering markedly the strength. Reducing the cooling rate after the solution treatment increases the amount of retained β-phase and changes the microstructure from a martensitic- to a basket-weave-type morphology. The strengths of these alloys are enhanced by dynamic strain aging (DSA) in the range ∼700–850K, and this is considered to derive from an interaction between silicon and interstitials which produces a strong interaction with mobile dislocations. Reducing the cooling rate after solution treatment and prolonged aging treatments remove silicon/rom the matrix solution and reduce the DSA effect.
Get full access to this article
View all access options for this article.