Laser rapidly fabricated amorphous/crystalline Mg-Zn-Ca biodegradable alloys: hetero-structure, corrosion behavior and antibacterial effect

Bioresorbable magnesium (Mg) alloy is known as revolutionary biomedical metal for orthopedic implants, despite the challenge of its too rapid degradation. In this study, laser powder bed fusion (LPBF) was employed to prepare amorphous Mg-Zn-Ca for biomedical application. By optimizing laser power and scanning speed, a near-fully dense part with a heterogeneous microstructure was achieved, consisting primarily of an amorphous matrix (>80%) with embedded nanocrystalline phases. Specifically, the molten pool zone exhibited a predominantly amorphous structure due to its cooling rate exceeding the critical value required for amorphous formation in Mg-Zn-Ca system. In contrast, the heat-affected zone underwent structural relaxation and initiated a partial crystallization. The amorphous/crystalline Mg-Zn-Ca owned relatively few of intermetallic or grain boundaries, leading to the formation of relatively dense and continuous Zn-rich protective layer, and effectively delayed the degradation of Mg matrix. Besides, it also demonstrated a favorable cytocompatibility, osteogenic capacity, and notable antibacterial efficacy. This work highlighted the promising potential of LPBF-processed amorphous/crystalline Mg-Zn-Ca as biodegradable bone implant with improved overall performance.