Asymmetrical mechanical behavior of a precipitation hardened beta titanium alloy

Precipitation hardened single crystals of a beta (bcc) Ti-40 at. pct V + 1.0 at. pct Si alloy have been deformed in compression at 77 K and 298 K. The dependence of the yield stress upon aging time at 843 K for solution treated crystals shows two maxima which are caused by silicide precipitates. The orientation dependence of the yield stress and of the active macroscopic slip plane have been determined as a function of aging time. The solution treated as well as aged crystals exhibit an asymmetry of both the yield stress and the plane of slip, the degree of asymmetry being larger at 77 K than at 298 K. The asymmetry of slip and yielding is not affected by the presence of precipitation hardening. The results indicate that the effect of the dislocation core structure on dislocation motion is independent of the presence of precipitates.