Effect of solution temperatures on microstructural evolution and deformation mechanisms of Mg-RE alloy prepared by laser direct energy deposition

Abstract

This study systematically investigated the microstructure evolution and mechanical properties of laser direct energy deposition (LDED) ZM6 alloy at different solution temperature. The results revealed that abnormal grain growth (AGG) occurred at 520 ℃ × 8h, resulting in grain coarsening and a sharp decrease in strength. The optimal solution treatment process is 470 ℃ × 8h, at which the microstructure is uniform and the strength is improved. The deformation mechanism shows a significant transformation with the appearance of AGG. When the grain grows normally, prismatic slip and pyramidal slip work together to bear large plastic strain. When AGG occurs, the deformation mechanism shifts to pyramidal slip and detwinning. These findings offer critical process guidelines and a scientific basis for governing AGG behavior and enhancing the strength of LDEDed Mg-RE alloys.

Keywords: Laser direct energy deposition, Magnesium alloy, Solution treatment, Abnormal grain growth, Deformation mechanism