Abstract:To investigate the influence of mold temperature on the temperature field and equivalent stress field of Mg alloy processed by inverse temperature field equal channel angular pressing (ITF-ECAP), a thermal mechanical coupled finite element analysis model was established for ITF-ECAP processing of B2 alloy (Mg-1.5Bi, wt%). Combined with experimental research, the processing process of B2 alloy at different mold temperatures was analyzed. The results show that during the ITF-ECAP, the temperature of the billet significantly increases at the corner of the mold channel, which facilitates smooth plastic deformation. After severe deformation, the temperature gradually decreases, thereby inhibiting coarsening of recrystallized grains. The stress concentration of the billet mainly occurs at the corner of the channel and near the mold outlet, and it significantly decreases with the increase in mold temperature. The experiment verification finds that when the mold temperature is low (200 ℃), the surface cracking of B2 alloy billet occurs after one-pass ITF-ECAP processing. In contrast, the surface of B2 alloy can be ITF-ECAP processed for four passes without surface cracking when the mold temperature is set as 300 ℃. Further microstructural characterization reveals that a bimodal grain structure composed of fine and ultrafine grains is formed after four-pass ITF-ECAP deformation, leading to a simultaneous improvement in both strength and ductility.