Influence of Friction Stir Processing Parameters on Microstructure, Hardness and Corrosion Resistance of Biocompatible Mg Alloy WE43

As a fourth-generation biodegradable material for biomedical applications, magnesium alloys are widely used for their light weight, low modulus, and biocompatibility, but their hardness and corrosion resistance need to be improved. AZ-series Mg alloys have been studied intensively. However, they contains Al which is hazardous to human health. WE43 Mg alloy is another promising alloy that is applied in automotive and aerospace for its corrosion resistance and stability at high temperatures (up to 300 °C). But its corrosion resistance in biological fluids is still lacking and needs further improvement. Friction stir processing (FSP) is a promising surface modification technique that able to refine the microstructure significantly and improves the corrosion resistance. In this research, the effect of rotational speed and traverse speed on the macro and microstructure as well as microhardness of Mg alloy WE43, and corrosion resistance in phosphate buffer saline, has been examined and determined. Subsequently, FSP parameters were analyzed and optimized by using response surface methodology with central-composite-design, and the mathematical models were obtained. The predicted results from models were consistent with the experiments. The SEM examinations showed that FSP reduced the average grain size from 6.64 μm for BM to as low as 4.32 μm. Additionally, the highest microhardness value was 87.1 HV (increase by 15.3%) at 1250 rpm and 30 mm/min. The best sample (B2) showed a reduction in corrosion rate compared with base metal by 5%. These results raise the potential of applying FSP to advance the application of WE43 for biomedical implants.