Fatigue Strength Improvement Effect of AZ31 Alloy by Multi-stage Wet Blasting

Magnesium alloys have a problem of low corrosion resistance and fatigue strength. In this study, we focused on multi-stage wet blasting (WB) as a method to improve the fatigue strength. This method is characterized by a smaller increase in surface roughness compared to ordinary WB. We compared normal WB with multistage wet blasting. Magnesium alloy AZ31 was used as the test specimen. Fatigue tests were performed by rotating bending fatigue test. In the multistage wet blasting, particles with large particle size were treated, and then particles with small particle size were used. As a result, the fatigue limit of WB125 and WB15, which are multi-stage treatments, increased by about 10% compared to the normal treatment. It was found that this was due to a 16% smaller surface roughness as well as a deeper surface modified layer. Furthermore, it was reconfirmed that the particle size used in the first stage was the dominant factor in imparting hardness and residual stress in the wet blasting process.