An insight into plastic deformation behavior of bimodal-grained Mg–1Mn–0.5Al–0.5Ca alloy

Mg–Mn–Al–Ca alloys with bimodal grain structures present excellent mechanical properties. In this work, a deeper understanding of the non-uniform deformation behavior of Mg–1Mn–0.5Al–0.5Ca alloys between bimodal and homogeneous grains was compared. The results showed that the bimodal grain structure of Mg–1Mn–0.5Al–0.5Ca alloy (MAX10505-Bim.) presented fine grains with an average grain size of about 1 µm, among which there are also long and coarse grains with a grain size of 20–40 µm. The homogeneous grains of Mg–1Mn–0.5Al–0.5Ca Mg alloy (MAX10505-Equ.) were equiaxial grains with an average grain size of 7 µm. The yield strength of the MAX10505-Bim. sample reached 360 MPa, elongation reached 11%, and a heterogeneous deformation-induced (HDI) stress of 199 MPa. In contrast, the MAX10505-Equ. sample showed a reduced yield strength of 151 MPa and an HDI stress of 94 MPa. During plastic deformation, the coarse grains were unfavorable to the basal slip, which provided an additional reinforcing effect, while the fine grains could coordinate the strain. The synergize effect with coarse grains and fine grains produced the high HDI stress, which leads to a significant increase in strength.