Prismatic Slip Mechanism Induced Grain Refinement in Mg-9Al-1Zn Alloy

Refining the grains of magnesium alloys can improve their mechanical properties. However, in compression at elevated temperatures, grain refinement and the absence of defects in a material are always incompatible. Although increasing the strain and strain rate or lowering the hot deformation temperature is beneficial for obtaining a fine grain size, it also increases the risk of defects such as cracks in the material. Therefore, the hot deformation behavior and grain refinement mechanism of the Mg-9Al-1Zn alloy are systematically studied in this paper. The results show that the deformation mechanisms of magnesium alloys are different when the lnZ values are at different intervals and that prismatic slip is more conducive to dynamic recrystallization than basal slip, which enables the material to exhibit a fine grain size after compression at elevated temperatures. When the Mg-9Al-1Zn alloy is hot deformed at 350 °C ≤ T ≤ 400 °C, 0.5 s−1 ≤ ε˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{\varepsilon }$$\end{document} ≤ 5 s−1, and ε = 0.8, its dominant grain refinement mechanism is prismatic slip, at which time the material has good hot processing properties and there is no risk of cracking during deformation. After compression at 400 °C/5 s−1, the grain size is only 3.8 μm, and the hardness is as high as 84.2 kgf/mm2. The results of this study have important theoretical significance for achieving grain refinement of magnesium alloys and further improving their properties.