Lightweight Medium Entropy Magnesium Alloy with Exceptional Compressive Strength and Ductility Combination

Abstract

The present study focused on the development of magnesium-based medium entropy alloy (Mg MEA). The multicomponent alloy with a composition, Mg62Li13Zn12Cu10Y3 (at.%), was processed using disintegrated melt deposition technique. The reported medium entropy alloys based on light metals, such as aluminum and magnesium, exhibit very low plasticity, and only cast alloys’ properties were investigated. Currently developed Mg MEA showed an appreciable plasticity of 13.9% in as-cast condition. Secondary processing such as extrusion was applicable on the cast alloy due to its high deformability. A change in intermetallics morphology from continuous pattern in cast alloy to discontinuous pattern in extruded alloy was observed. In line with the change in microstructure, remarkably improved compressive properties were realized in extruded alloy as compared to cast alloy. Compressive strength and plasticity increased from 444 MPa and 13.9% in cast alloy to 675 MPa and 32.7% in extruded alloy. Previously reported lightweight MEAs exhibited a limited plasticity up to 6.5% in the cast form. The current lightweight Mg MEA reached a plasticity of more than twice of cast alloy and more than five times in the case of extruded alloy when compared to reported MEAs’ plasticity in open literature. Unlike reported MEAs, currently developed Mg MEA revealed a relatively simple microstructure with three major phases. From the alloy design perspective, a large atomic size difference (δ: 8.49%) in the alloy was the main cause for the intermetallic formation. However, multiple phase formation was mitigated due to the suitable mixing enthalpy (ΔHmix: −\u20094.52 kJ/mol). This counterbalancing effect from mixing enthalpy led to a simple microstructure, thereby enhancing the mechanical properties in the currently developed Mg MEA.