Dislocation density model for the effect of grain size on the flow stress of a Ti-15.2 at.% Mo β-alloy at 4.2-650 K

Hall-Petch (H-P) plots of the effect of grain size d = 4.6-22 μm on the flow stress σ at 4.2-650 K of a β-Ti-15.2 at.% Mo alloy gave that the parameter σi increased with strain ɛ and with decrease in temperature T. In contrast, the parameter KH-P was relatively independent of ɛ and T. The corresponding dislocation density ρ increased with ɛ and with decrease in d, giving the well-known relation σ/M ≈0.5 μbρ1/2, where M is the Taylor factor. The magnitudes of σi and KH-P calculated from ρ were in reasonable agreement with those obtained from the H-P plots. The grain size dependence of σ was in accord with Li's grain boundary ledge mechanism.