The effect of friction stir process on the mechanical, tribological, and biocompatibility properties of AZ31B magnesium alloy as a biomaterial: A pilot study.

Recently, AZ31B magnesium alloy has been widely employed in automotive, aerospace, and bio implant industries due to its light-weight and biocompatibility properties. However, the equilibrium of ductility and strength of this material and the negativity brought by its poor wear behavior have limited its versatile use. Friction stir processing (FSP) has been commonly used as severe plastic deformation method for improving mechanical and tribological properties of metal sheets. The effect of this method on the biocompatibility of materials is a matter of curiosity that should be emphasized. So, the present study aims to investigate the effect of friction stir process on the mechanical, tribological, and biocompatibility properties of AZ31B magnesium alloy. It is observed that FSP enhanced the tensile properties of the alloy but decreased its elongation. It was determined that the base material exhibited ductile character on the fracture surface of the specimens, and mixed ductile/brittle fracture was evident with the FSP. In the FSP zone, the hardness value was improved by 17% compared to the base material. Also, the wear performance of the alloy enhanced in ambient air and Simulated Body Fluid (SBF) solution. Wear properties in SBF solution were better due to less adhesive bonds between the friction surfaces. This assessment was supported by SEM images of the wear path and surface of counter bodies. On the other hand, FSPed AZ31B alloy materials with improved strength properties were not cytotoxic for human gingival fibroblasts, and these results may suggest that the materials are safe for clinical uses.