Effect of Extrusion Temperature on the Microstructure and Properties of Biomedical Mg-1Zn-0.4Ca-1MgO Composite

The effects of extrusion temperatures on the microstructure, mechanical properties, and corrosion performance of biomedical Mg-1Zn-0.4Ca-1MgO composites were systematically investigated. The results indicated that lower extrusion temperatures notably refined the grain size and promoted the formation of numerous nano-scaled secondary phase particles. The grain sizes were 0.8 μm, 1.7 μm, and 3.4 μm for the materials extruded at 280 °C, 310 °C, and 330 °C, which were named ET280, ET310, and ET330. The finest grain size and abundant precipitates enhanced the mechanical properties of the composite with a microhardness of 86.9 HV, a yield strength of 305 MPa, and a fracture elongation of 15.2%. Moreover, the ET280 alloy with ultra-fine grains exhibited the optimal corrosion resistance among these three composites, and its annual corrosion after immersion in Hank’s solution for 14 days was only 0.17 mm/y. The excellent performance in vitro immersion was mainly attributed to the formation of the uniformly dense Ca-P layer on its surface and the contiguous compact Mg(OH)2layer, which could effectively weaken the contact between the corrosive solution and the Mg matrix.