Features of β-Phase Decay in Ti–22Nb–6Zr Alloy

Abstract

Abstract—A compact powder Ti–22Nb–6Zr alloy was obtained by powder metallurgy methods. The initial alloy powder was synthesized by the calcium hydride method. It was shown that, after consolidation during vacuum sintering and subsequent hot isostatic pressing, the residual porosity of the consolidated material did not exceed 1%. The physicomechanical properties and structural features of the powder alloy obtained were investigated. It was established that, after hot isostatic pressing, there was no release of brittle ω phase in the structure of β-Ti alloy. In the range of heating temperatures of 550–700 K, the β phase was prone to decay with the formation of the α phase of a lamellar morphology and a small amount of the ω phase. The appearance of decay products was accompanied by dilatometric effects and an increase in Young’s modulus. It was shown that, regardless of the method of powder consolidation, the resulting alloy exhibited elinvarity (a small change in Young’s modulus with increasing temperature) in the temperature range of 200–500 K. It was determined that, at room temperature, samples with ~8% pores had Young’s modulus of about 64 GPa; when the porosity level was reduced to <1%, Young’s modulus increased to 73.5 GPa.