Effects of Heat Treatment on Microstructure, Mechanical Properties, Corrosion Resistance and Cytotoxicity of ZM21 Magnesium Alloy as Biomaterials

The effects of heat treatment on microstructure, mechanical properties, corrosion resistance and cytotoxicity of extruded Mg-2Zn-1Mn (wt.%) alloy were investigated for biomedical application in this study. The extruded alloy was T4 treated at 510 degrees C for 4h and T5 treated at 200 degrees C for 16h separately. The extruded Mg-Zn-Mn alloy mainly consists of MgxMny phases. After T4 treatment, the amount of MgxMny phases decreases and average grain size rises from 8 to 24m. After T5 treatment, Mg7Zn3 phase newly precipitates along the grain boundaries and the size of grain remains similar. Compared with the T4-treated samples, the extruded and T5-treated samples exhibit higher mechanical properties. The T5-treated samples have an ultimate tensile stress of 273MPa and an elongation of 19.7%. On the other hand, T4-treated samples present higher corrosion resistance in electrochemical tests. The degradation rates of extruded, T4-treated and T5-treated samples are 0.44mm/year, 0.48mm/year and 0.50mm/year, respectively, in Ringer's solution at 37 +/- 0.2 degrees C. In addition, T4-treated alloy does not induce toxicity to the L-929 cells in in vitro cytotoxicity test.