Improving stress corrosion cracking resistance of AZ31 magnesium alloy in Hanks? solution via phosphate conversion with laser shock peening pretreatment

The present work aims to improve stress corrosion cracking (SCC) behavior of AZ31 magnesium alloy in Hanks' solution via laser shock peening (LSP) and subsequent phosphate conversion (PC). The surface and cross section morphology, microstructure and scratch behavior of coated samples were characterized with and without LSP pretreatment. Additionally, immersion, electrochemical corrosion and stress corrosion tests in Hanks' solution were conducted to evaluate the suitability of LSP and PC composite processing for improving corrosion resistance and the stress corrosion susceptibility of AZ31 magnesium alloy in Hanks' solution. The experimental results showed that the grain refinement and high specific area generated by LSP promoted the deposition of coating and then improved the scratch resistance of coating. The LSP/PC composite coating significantly enhanced the corrosion resistance and mechanical properties of AZ31 magnesium alloy in Hanks' solution, which was attributed to the dense coating formed by PC reaction and the strain strengthened layer induced by LSP pretreatment on the sub-surface of the material.