A polycrystal plasticity based thermo-mechanical-dynamic recrystallization coupled modeling method and its application to light weight alloys

Hot forming often has to be resorted when processing metals with limited room-temperature formability, such as aluminum, magnesium, etc. The temperature rise induced by plastic work, especially under high strain rates, can exert significant effect on mechanical response as well as dynamic recrystallization of deformed metals. In the present work, a polycrystal plasticity based thermo-mechanical-dynamic recrystallization (DRX) coupled approach is established by implementing thermo-mechanical effect in a VPSC-DRX model where a grain nucleation and growth model is implemented into the VPSC framework. The modeling parameters associated with various slip modes, temperatures and strain rates are calibrated by isothermal compression experiments, and then evolution functions of hardening and DRX related parameters with respect to temperature and strain rate are established. The integrated computation of plastic deformation, texture, grain size and temperature update in hot deformation of metals can be achieved. The proposed method is verified and then applied to simulate hot extrusion processes of magnesium alloy bars at three different ram speeds. The influences of ram speed on development of deformation texture and grain size are analyzed. The temperature rise due to plastic work enhances stress softening and stimulates grain growth, makes the macro/micro responses of materials no longer monotonically varied with strain rate.