Phase formation and strengthening mechanism of Zn–2 wt%Cu alloy fabricated by laser powder bed fusion

Biodegradable Zn-based alloys with stable degradation rates and excellent biocompatibility have numerous potential applications as orthopedic implant materials. In this study, a Zn–2 wt%Cu alloy is fabricated through laser powder bed fusion (LPBF), and its microstructural evolution, mechanical properties, and strengthening mechanism are investigated. The microstructure comprises equiaxed grains with an average grain size of 0.2 μm, and the phase is composed of supersaturated η-Zn phase, ε-CuZn₅ phase, and a small amount of γ-Cu₅Zn₈ phase. The phase formation sequence during rapid solidification is γ-Cu₅Zn₈→ε-CuZn₅→η-Zn. The hardness, yield strength, and ultimate tensile strength are increased by solution strengthening, fine-grain strengthening, and second-phase strengthening (hardness up to 84.78 HV, yield strength = 145.18 MPa, and ultimate tensile strength = 188.17 MPa). The solidification behavior and microstructure of the LPBF Zn–2 wt%Cu alloy are elucidated, providing a theoretical foundation for the design of biodegradable Zn-based alloys via LPBF.