Effect of severe shot peening on corrosion behavior of AZ31 and AZ91 magnesium alloys
Abstract Severe shot peening (SP) was performed on the AZ31 and AZ91 Mg alloys to obtain a nanostructured surface layer. The microstructure, micro hardness and corrosion behavior of AZ31 and AZ91 Mg alloys after SP treatment were studied using transmission electron microscopy, micro hardness tester and corrosion tests, respectively. Results showed that SP treatment produced a plastic deformation layer with a Mg grains at the nanometer scale in the surface of AZ31 and AZ91 Mg alloys. After SP treatment, the micro hardness in the near surface region displayed an obvious increase for two alloys, owing to the combination of the grain refinement and the work hardening. The corrosion resistance of AZ31 alloy was improved by SP treatment, because a relatively compact passive film formed rapidly on the nanostructured surface. Unfortunately, SP treatment played a minor role in enhancing the corrosion resistance of AZ91 alloy, because it had little effect on size and distribution of b phases.