Effect of strain-integration gas-infusion casting process and post-treatment on the corrosion behavior of AZ91 alloy

Abstract

AZ91 magnesium alloy casting is essential for lightweight automotive, aerospace, and electronics applications. This alloy accounts for 90 % of the applications of magnesium alloys. However, AZ91 castings typically exhibit a coarse dendritic microstructure and a brittle β-phase, which diminish their mechanical performance and limit their industrial applications. The Strain-Integrated Gas Infusion (SIGI) casting process has been explored to address these challenges. The SIGI casting process produces refined microstructure and eliminates microporosity. This study investigates the effect of the SIGI casting process on the corrosion resistance of AZ91 magnesium alloy. A comparative analysis was conducted to assess the impact of different casting processes, namely SIGI, Stir casting, and Conventional die casting, on the corrosion behavior of AZ91 magnesium alloy. The three casting methods were followed by solution treatment and subsequent aging, and the effects of these treatments combined with the casting processes were also examined. Microstructural characterization and mechanical testing were performed at each stage. Additionally, weight loss measurements and electrochemical behavior tests were conducted to evaluate the corrosion behavior under all conditions SIGI process enhanced the mechanical properties and corrosion resistance of AZ91 alloy, with peak-aged SIGI casting showing 280–300 MPa strength, 5–6 % ductility, and a corrosion rate of 0.011 mm/year, compared to conventional casting with 100–200 MPa strength, 2–3 % ductility, and 0.107 mm/year corrosion rate. The underlying mechanisms contributing to these improvements were also explored. The results confirm the effectiveness of the SIGI casting process in enhancing the corrosion resistance of AZ91 alloy, providing valuable insights for industrial applications.