Synthesis of Magnesium Alloy Surface Composites by Friction Stir Processing

Abstract

Magnesium alloys are one of the candidate materials for bioimplant applications. However, their rapid corrosion in physiological environments with hydrogen gas evolution results in the lethal subcutaneous gas accumulation. In addition, the higher corrosion rate diminishes the mechanical newlinestrength of the bioimplant. Hence, investigations on the mechanical and corrosion behaviour of the magnesium alloys (base material - AZ91D alloy) in corrosive physiological environment becomes newlineobligatory. Tailoring the microstructure improves the nobility, corrosion resistance, and hence minimizes the strength degradation of AZ91D alloy. Friction stir processing (FSP) because of its unique material flow characteristics and ability to tailor the microstructure improves the mechanical, corrosion, and tribological properties of the newlinealloy. The peak temperature attained by AZ91D alloy in the course of FSP influences the dynamic recovery and dynamic recrystallization (microstructure evolution). A numerical model is developed to explore the influence of FSP process parameters on the peak temperature attained in the course of FSP of AZ91D alloy. The results of the numerical model indicates that tool rotation newlinespeed, tool traverse speed and shoulder diameter majorly influence the thermal phenomenon during FSP of AZ91D alloy. The simulation results are utilized to obtain the range of FSP process parameters for experimental trials. AZ91D alloy is friction stir processed by varying the process parameters as per the design matrix. newlineThe microstructure, surface roughness, microhardness, and corrosion rate (in normal simulated body fluids and inflammatory simulated body fluids) of AZ91D alloy and friction stir processed AZ91D alloy are characterized. The results indicate that the grain refinement and dispersion of sub-micron and#946; phase improve the microhardness, corrosion resistance, and biocompatibility of newlinefriction stir processed AZ91D alloy in comparison to AZ91D alloy.