Development of Wrought Mg Alloys Via Strip Casting

Abstract

Development of wrought Mg alloy, particularly in sheet form, are essential to support the growing interest for lightweight components in the automotive industry. However, development of Mg alloy sheets has been quite slow due to the complexity of sheet production originated from limited deformability of Mg. In this respect, strip casting, a one-step processing of flat rolled products, can be an alternative for the production of Mg alloy sheets. In this study, AZ31 and experimental alloys are strip cast into 2 mm thick strips. The microstructure of the as-cast AZ31 alloy strip consists of columnar zones near the roll side and equiaxed zones in the mid-thickness region. On the other hand, as-cast MX1 alloy strip shows equiaxed dendritic structure through the thickness of strip. The cooling rate estimated from the secondary dendrite arm spacing is around 102 K/s. These alloys were subjected to various thermomechanical treatments and their tensile properties were evaluated. Strip cast AZ31 alloy in H24 condition has equivalent yield and tensile strengths with similar ductility compared to commercial ingot cast AZ31-H24 alloy, indicating that strip casting is a viable process for the fabrication of Mg alloy strips. The experimental MX alloys have a large volume fraction of fine dispersoid particles in the microstructure, resulting from the beneficial effect of strip casting on microstructural refinement. It has been shown that the experimental MX0 alloy has superior tensile properties compared to commercial ingot cast AZ31-H24 alloy, suggesting the possibility of the development of new wrought Mg alloy sheets by strip casting.