Influence of test temperature and microstructure on the tensile properties of titanium alloys

Tensile tests were performed between room temperature and 500 °C on age-hardened Ti-Al and Ti-6A1-4V alloys to study the effect of various microstructural parameters on the temperature dependence of the yield stress. It was found that the concentration of interstitial solute atoms is responsible for the strong temperature dependence of the yield stress. Small interstitial concentrations increase the yield stress significantly at low test temperatures, while this hardening effect almost disappeared at temperatures above about 300 °C. Through variations of degree of age-hardening, grain size, texture, phase morphology, and phase dimensions of (α + β) microstructures, the absolute yield stress values were changed by constant amounts over the test temperature range without changing significantly the temperature dependence. The yield stress increased by increasing the degree of age-hardening, by decreasing the grain size or phase dimensions, by texture hardening, and by choosing equiaxed instead of lamellar phase morphologies.