Additive Manufacturing of ZK60 Magnesium Alloy by Selective Laser Melting: Parameter Optimization, Microstructure and Biodegradability

Mg-Zn-Zr (ZK60) magnesium alloy samples were prepared by selective laser melting (SLM). The processability of ZK60 prepared by SLM was thoroughly investigated via varying the laser processing parameters. Experimental results show that laser power and scan velocity played an important role in determining the quality of SLM ZK60. SLM ZK60 with minimal defects and high dimensional accuracy could be obtained at a laser power of 50 W and scanning velocity of 500-800 mm/s. The formation mechanisms of pores were also identified and illustrated thoroughly in size and shape in the transition regimes. Significantly refined grains were observed in SLM ZK60, with an average grain size (G(a)) of 7.3 mu m for SLM ZK60 versus 56.4 mu m for cast ZK60. Besides the alpha-Mg phase, the Mg7Zn3 eutectic phase was precipitated in the a-Mg matrix in SLM ZK60, and the MgZn phase in cast ZK60. The hardness of cast ZK60 and SLM ZK60 was 0.55 and 0.78 GPa, respectively, with similar elastic modulus. SLM ZK60 exhibited a higher corrosion resistance in Hanks' solution compared with cast ZK60 as indicated by a decrease of about 30 % in hydrogen evolution rate and of about 50 % in the corrosion current density. The SLM ZK60 fabricated in the present study exhibits a great potential for biomedical applications due to desirable mechanical properties and a reasonably low degradable rate.