Effect of phase transition caused by different treatment process on mechanical properties of powder metallurgy Ti-22Al-24Nb-0.5Mo (at.%) alloys

Abstract

The microstructural evolution and mechanical properties of powder metallurgy (PM) Ti-22Al-24Nb-0.5Mo prepared by combination of hot isostatic pressing (HIP), ring rolling, and heat treatment were investigated. The density and micropore distributions of PM alloys under HIP are relatively homogeneous. Ring rolled and solution treatment in the (α2 + B2 + O) region led to the refinement of grain size and long lath O phase and α2 phase mostly located at the grain boundaries. Aging treatment in the (B2 + O) region caused the occurrence of peritectoid reaction B2 + α2 → O owing to the segregation of the Nb element and refined the acicular O phase. The mechanical properties of PM alloys varied with the size and volume fraction of O phase and α2 phase. The long lath O phases improve the elongation and acicular O precipitates are benefit to the elevation of alloy strength.