Mechanical anisotropy and microstructural heterogeneity of a free-forged ME20 alloy with a large cross section

Abstract

In this work, the mechanical anisotropy and microstructural heterogeneity of the large-sized Mg-1.5Mn-0.3Ce (wt.%, ME20) forging samples are thoroughly investigated. As-forged ME20 sample presents inhomogeneous microstructure with gradient variations of grain size, dislocation density, and texture intensity from the edge to the center positions due to the gradient accumulation of strain and temperature during forging. Despite of that, nearly the same tensile yield strength (TYS) was obtained from the edge to the center positions, which can be mostly ascribed to the combined effects of fine grain, sub-grain, precipitate, texture, and residual dislocation. In addition, as-forged ME20 sample shows an enormous disparity of TYS between the forging direction and lengthening direction, with the TYS difference of ∼200 MPa, which is primarily associated with the strong texture that dominates the activation of twinning/slipping modes. Therefore, the high level of mechanical anisotropy appears to be only sensitive to strong basal texture, whereas the heterogeneous microstructure does not induce obvious mechanical properties variation along gradient positions. These results can offer fundamental insight into further improving mechanical properties of Mg forging components with large cross-section.