Effect of Rare Earth and Ca Micro-Alloying on the Microstructure and Anisotropy of AZ31 Magnesium Alloy Sheets

Abstract

AZ31 magnesium alloy sheets can be applied as 3C electronic product shells. However, AZ31 sheets exhibit obvious anisotropy, which limits their industrial application range. The composition modification of AZ31 is a good choice to improve the anisotropy of the sheets, but the effect of the multi-element micro-alloying on the microstructure and anisotropy of AZ31 alloy sheets is still less investigated. For this aim, the plasticity and anisotropy of AZ31 sheets after adding Ca and rare earth elements such as Y and Gd were investigated in this paper. It is found that, different from the alloying role of single Ca or Ca and Y, the composite addition of 0.2Ca and 0.2Gd can obviously enhance the anisotropy of AZ31 alloy sheets. As a result, the elongation of AZ31 in the rolling direction (RD) direction, 45° direction, and transverse direction (TD) direction is increased from 12.5% to 22%, from 5% to 18.5%, and from 1.5% to 8.5%, respectively. This can be explained as follows: the Al8Mn4Gd phase formed by the addition of Gd consumes a lot of Mn, thus avoiding the formation of brittle phases Al8Mn5 and leading to the improved mechanical properties of the alloy sheets. This study will offer a good solution for enhancing the formability of AZ31 sheets under the condition of not significantly increasing the production costs.