Microstructural Evolution and Mechanical Properties of AE45-Gd Magnesium Alloy Under Different Aging Processes

To investigate the microstructural evolution and mechanical property changes in an as-extruded AE45-Gd magnesium alloy subjected to different aging treatments, an alloy containing multi-scale second phases was prepared by extrusion and subsequently subjected to artificial aging and aging under pressure. The microstructural evolution, age-hardening behavior, and mechanical properties of the alloy under different aging treatments were investigated. It was found that conventional isothermal aging can improve the mechanical properties to a certain extent. As the aging temperature increases, the peak-aged hardness decreases slightly, while the time to reach peak aging is progressively shortened. Aging under pressure also significantly shortens the time to peak aging, though the peak-aged hardness changes little. The multi-scale second phases in the alloy, consisting of coarse blocky Al2RE (La, Ce, Gd) and fine granular Al11RE3 (La, Ce, Gd), exhibit typical Ostwald ripening during aging, and aging under pressure accelerates this process. The optimum aging parameters are determined to be 200 °C for 16 h. After this treatment, the alloy achieves a yield strength of 183.95 MPa, a tensile strength of 322.50MPa, and an elongation of 4.32%. Microcracks predominantly initiate at the large Al2RE (La, Ce, Gd) compounds. The small granular Al11RE3 (La, Ce, Gd) particles show little evidence of self-cracking, and cracking mainly occurs at the phase boundaries between these particles and the magnesium matrix.