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

Dislocation Density Model for the Effect of Grain Size on the Flow Stress of a Ti–15.2at%Mo β-Alloy at 4.2–650K. K.H.Chia, K.Jung, H.Conrad: Materials Science and Engineering A, 2005, 409[1-2], 32-8