Implementation of Balanced Strength and Toughness of VW93A Rare-Earth Magnesium Alloy with Regulating the Overlapping Structure of Lamellar LPSO Phase and \(\beta^{\prime }\) Phase

Abstract

Although extensive research has been conducted on the strengthening mechanism of rare-earth magnesium alloys, achieving a balance between strength and toughness has proven challenging. This paper introduces a method for regulating the overlapping structure of the lamellar long-period stacking ordered (LPSO) phase and \(\beta^{\prime }\) phase to achieve a balance between strength and toughness in the alloy. By focusing on the extruded VW93A alloy cabin component, the study delves into the mechanism of the alloy's strength and toughness through a comparative analysis of the microstructure characteristics and room-temperature mechanical properties of the alloys in various states. Additionally, the molecular dynamics simulation is employed to clarify the mechanism of the alloy's strength and toughness balance induced by the overlapping structure. The findings reveal that when the \(\beta^{\prime }\) phase precipitates in the alloy alone, a significant increase in strength is achieved by pinning dislocations, albeit at the expense of reduced plasticity. Conversely, the presence of the lamellar LPSO phase disperses dislocations between the LPSO phase lamellae, thereby enhancing plasticity by avoiding stress concentration resulting from dislocation stacking. When both phases coexist in the alloy and form an overlapping structure, the dispersion of dislocations due to the lamellar LPSO phase weakens the pinning effect of the \(\beta^{\prime }\) phase, further reducing dislocation stacking and resulting in a balance of strength and toughness in the alloy. Ultimately, the alloy with the overlapping structure exhibits an ultimate tensile strength and elongation of 421 MPa and 20.1%, respectively.