Hot deformation behavior and resultant microstructural evolution of dilute Mg–Bi–Sn–Mn alloy during hot compression

Abstract

This study investigated the dynamic recrystallization (DRX) mechanism and hot-deformation behavior of the solution-treated Mg-0.5Bi-0.5Sn-0.5Mn (BTM000) alloy during hot compression at temperatures ranging from 175 to 225 °C with a strain rate of 0.001–1 s−1. Processing maps and constitutive equation were used for a detailed analysis. The results showed a strong correlation with a coefficient of 0.987669, indicating the accuracy of proposed method in predicting the hot deformation behavior. The average activation energy (Q) was found to be 139.10 kJ/mol, and the stress component (n) was calculated to be 7.96, suggesting that cross-slip is the primary deformation mechanism. Based on the processing maps, the most suitable processing conditions were found to be within the range of 210–290 °C with a strain rate of 0.37–1 s−1. At a low strain rate of 0.001 s−1, the dominant deformation mechanism observed was pyramidal <c+a> slip. However, at higher temperatures (175–325 °C) and a strain rate of 1 s−1, a transformation from basal <a> slip to a combination of basal <a> slip and pyramidal <c+a> slip was observed. Under low-temperature and low-strain-rate conditions (175 °C/0.001 s−1), continuous dynamic recrystallization (CDRX) was the dominant mechanism. In contrast, under other deformation conditions (175 °C/1 s−1, 325 °C/0.001 s−1, 325 °C/1 s−1), a synergistic effect between discontinuous dynamic recrystallization (DDRX) and CDRX was evident. Through quasi-situ kernel average misorientation (KAM) characterization, it was observed that the local storage energy associated with CDRX was significantly lower compared to the combination of CDRX and DDRX, indicating a higher likelihood of CDRX occurrence.