A strain integrated gas infusion process (SIGI) for magnesium alloy castings

Abstract

This study presents a Strain Integrated Gas Infusion Process (SIGI) to manufacture high-performance cast AZ91 magnesium alloys without the addition of secondary alloying elements/reinforcements or secondary processing. The current SIGI process involves a combination of agitation and localized rapid heat extraction via strain integration and high-energy gas infiltration. The SIGI casting process has been compared systematically with conventional techniques. The critical process parameters, including hole diameter, bubble diameter, and flow rate, have been optimized through numerical calculations, simulations, extensive experiments, and comprehensive analysis. The study also focused on investigating the effect of gas bubbles on the molten metal and established the mechanisms involved in improved solidification. Gas infusion combined with strain integration impacts the solidification process, ensuring uniform alloying element distribution and reducing segregation and microporosity. This manufacturing strategy eliminates casting defects such as segregation and microporosity, resulting in a non-dendritic homogeneous microstructure. The significant refinement in morphologies of both primary (α-Mg dendrites) and secondary (β-Mg₁₇Al₁₂ phase) phases highlights the success of the current SIGI process. Compared to the conventional casting processes, a remarkable improvement in strength-ductility synergy is achieved in the current SIGI process. The scientific know-how and efficiency of the current SIGI process are established and discussed in detail, providing a promising solution to address the existing challenges encountered in magnesium alloy billet castings. The SIGI process improves the mechanical properties and corrosion resistance of billet-cast magnesium alloys. The SIGI process is suitable for the billet casting, offering significantly improved properties but faces limitations in complex mold casting applications. The billets casted by SIGI process can be used as a high-quality precursors for downstream processes to create industrial components.