Deformation Behavior of Mg Alloys under Uni-axial Tensile Loading and Stretch Forming

Abstract

There has been a growing interest in Mg alloys due to their excellent specific strength and stiffness. Such properties of Mg alloys are quite attractive for applications in transportation systems which require light-weight systems. Most of the Mg alloys currently in use in transportation systems are cast products. However, Mg sheet products are much needed since they have a larger potential for applications than their cast counterparts. It has been recently shown that the application of twin-roll casting (TRC) can effectively produce low cost Mg alloy sheets with the equivalent tensile properties to those of conventionally processed alloy sheets. Due to its relatively fast solidification rate, TRC can provide beneficial effects on microstructure such as refinement of microstructural features, extension of solid solubilities, and formation of metastable or non-equilibrium phases. It is well known that Mg alloy sheets typically exhibit strong basal textures after thermomechanical treatment and such strong basal texture has an adverse effect on their formability at room temperature. Therefore, there have been numerous studies on modifying the texture of Mg alloy sheets to a weaker and more random distribution of basal poles by the addition rare earth (RE) elements and it has been demonstrated in several studies that the weakening of texture significantly improves the formability of Mg alloy sheets at room temperature. However, the cost of RE elements is too expensive to satisfy the needs of automobile companies or other transportation companies. Among various Mg alloy systems subjected to extensive studies, Mg-Zn-Ca and Mg-Al-Sn alloys, non-containing RE elements, are quite interesting since they have a considerable formability similar with Al alloys at room temperature. The present work attempts to clarify the deformation behaviors of two alloys (ZX11 alloy and AT31 alloy) by comparing with commercial AZ31 alloy under uni-axial and bi-axial loading.