Viscoplastic behavior of ultrafine-grained alloys

Features of mechanical behavior of ultrafine-grained (UFG) titanium and aluminum alloys under quasi-static and shock wave loading with amplitudes up to 10 GPa were studied by the numerical simulation method. To describe viscoplastic behavior of alloys, a multilevel model is offered. The model takes into account several structural factors influencing the mechanical behavior of coarse-grained and UFG alloys. The results display that the strain rate sensitivity of the yield stress of UFG and polycrystalline titanium alloys is significantly different in the range from $10^{-3}$ to $10^6$ s$^{-1}$. The visco-plastic behavior of UFG FCC and HCP alloys is shown to be different at high strain rates.