Strategy for suppressing abnormal grain growth of ZK60 Mg alloy during solution by pre-compression: A quasi-in-situ study

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Abnormal grain growth (AGG) easily takes place in Mg alloys during high-temperature solutions, resulting in deterioration of mechanical properties. Hence, the compression prior to solution (pre-compression) was conducted to suppress AGG, and the microstructure evolution as well as suppressing mechanisms was investigated based on quasi-in-situ analysis. After compression along the transverse direction, <11–20>//ED grains preferentially nucleated and rapidly grew up, and the initial <10–10>//ED texture was weakened. Two grain growth modes of heat-induced and strain-induced grain boundary migrations were found. The former was attributed to the high interfacial energy of grain boundaries with large curvature. The latter consumed the adjacent grains with high storage energy, forming abnormal grains with irregular shapes. The compression with a reduction > 6% could obviously suppress AGG. The suppressing effects were mainly attributed to weakening the size advantage of <11–20>//ED grains, increasing nucleation, reducing grain boundary character distribution, and redistributing storage energy distribution. After 12% compression along the transverse direction, 30° misorientation of <11–20>//ED grains and high energy grain boundaries were reduced. The {10–12} tensile twins and {10–15} high index twins induced by compression increased the nucleation of static recrystallization. Beside, compression introduces high-density dislocations, which also contributed to suppressing AGG behavior during solution.