Xueqing Wu, Yilong Dai, Jianguo Lin
To overcome the limitations of low strength and limited solubility of alloying elements in biodegradable Zn alloys, a Zn–0.7Mg (wt.%) alloy was selected as the research subject. The as-cast alloy was subjected to solid solution treatment at 360 °C for 1 h under a pressure of 5 GPa, followed by aging at 150 °C for 30 min, and finally cold-rolled at room temperature with an 80% reduction in thickness. The microstructural evolution of the alloy during high-pressure solid solution treatment, aging, and cold rolling was systematically characterized, and its influence on mechanical properties was investigated. The results indicate that high pressure significantly enhanced the solubility of Mg in the Zn lattice, resulting in a microstructure composed mainly of a supersaturated α-Zn phase containing approximately 0.67% Mg, with only minor amounts of eutectic structure (Mg 2 Zn 11 + α-Zn) retained at grain boundaries. After aging at 150 °C for 30 min, numerous nanoscale Mg 2 Zn phases precipitated uniformly within the matrix and along grain boundaries. Subsequent cold rolling with 80% reduction led to the formation of a fine dynamic recrystallization structure. This refined microstructure is attributed to the presence of finely dispersed Mg 2 Zn phases, which promote recrystallized grain nucleation via the particle-stimulated nucleation (PSN) mechanism and inhibit grain boundary migration. As a result, the processed alloy exhibited significantly enhanced strength and ductility, achieving a tensile yield strength of 305 ± 7 MPa, an ultimate tensile strength of 360 ± 8 MPa, and an elongation of 39.4 ± 1.3%.