Laser printed amorphous magnesium alloy: Microstructure, mechanical properties and degradation behavior

Amorphous magnesium (Mg) alloy, especially Mg-Zn-Ca series, has been receiving continuous attention in biomedical field, because of its favorable corrosion resistance, suitable modulus and biocompatibility. In this work, laser powder bed fusing (LPBF) with unique characteristics of rapid solidification and layer-by-layer fashion was used to fabricate bulk Mg-Zn-Ca and Mg-Zn-Ca-Y amorphous parts. It was revealed that the as -built parts contained amorphous structure, since the molten pool experienced an extremely high cooling rate that suppressed ordered arrangement of atoms. A few of nanocrystals (alpha-Mg and Ca2Mg5Zn13) were obtained due to repeated heat accumulation in heat-affected zones. More significantly, Y alloying altered the glass forming ability and stimulated in-situ formation of quasicrystal I-phase with high hardness and elastic modulus, which not only acted as reinforced particles, but also retarded the propagation of shear bond and thereby excited the emergence of secondary shear bands and vein patterns. Thus, Mg-Zn-Ca-Y part exhibited simultaneously improved yield strength and plasticity. Despite the micro galvanic corrosion induced by crystalline phases, it exhibited a moderate corrosion rate. Furthermore, in vitro cell tests proved its favorable biocompatibility. Our work highlighted the feasibility to prepare amorphous Mg alloy with controllable performance.