Effect of heat treatment on microstructure, mechanical, corrosion and biocompatibility of Mg-Zn-Zr-Gd-Nd alloy

Pure Mg and prealloyed Mg-Gd-Nd-Zr-Zn alloy samples were prepared using powder metallurgy route and further heat treated. The effects of heat treatment on the microstructure, mechanical, corrosion resistance and biocompatibility properties of these samples were investigated. Microstructural analysis showed α-Mg matrix with secondary phases like Mg₃Gd/Nd, Mg₁₂Gd/Nd and Mg₄₁Nd₅ in the Mg alloy. After heat treatment, 250 °C for 12 h, both samples showed improvement in the hardness and compressive strength due to rearrangement of the secondary phases and grains. However, the hardness and compressive strength of Mg alloy (54 ± 5 HV and 239 ± 23 MPa) was higher than pure Mg, which were further improved with heat treatment (61 ± 4 HV and 260 ± 21 MPa). The corrosion potential of Mg alloy was more positive (−1.51V) than pure Mg (−1.61V) signifying its better resistance to corrosion initiation. However, the Mg alloy exhibited higher corrosion current than pure Mg due to galvanic effect of secondary phases. In vitro tissue culture experiments demonstrated good biocompatibility of both samples and therefore present high strength Mg alloy can be better choice as biodegradable implants.