Effect of Phase Transition caused by Different Treatment Process on Mechanical Properties of Powder Metallurgy Titanium Alloys

The microstructural evolution and mechanical properties of powder metallurgy Ti-22Al-24Nb-0.5Mo prepared by combination of hot isostatic pressing, ring rolling, and heat treatment were investigated. Ring rolled and solution treatment in the (α₂ + B2 + O) region led to the refinement of grain size and long lath O phase and α₂phase 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.