Effect of Shear Angle on Microstructure and Mechanical Properties of AZ61 Mg Alloy During Extrusion-Shear Process

To enhance the strength and plasticity of the AZ61 Mg alloy, a process called extrusion-shear (ES) was proposed. The process is based on conventional extrusion with the addition of two equal extrusion channels (ECAP). ES process is a severe plastic deformation process that can effectively enhance the microstructure and mechanical properties of Mg alloy. However, the impact of shear angle on the process and mechanism remains unclear. Two channel angles, 120 and 135°, were designed for processing. The properties of the center and edge zones of the formed billets were investigated. This process is performed on AZ61 Mg alloys in the as-cast state with a processing temperature of 440 °C. The results show a significant increase in strength, with the yield strength reaching 193 MPa in the center zone of the ES-135° sample and the ultimate tensile strength reaching 241.9 MPa in the edge zone of the ES-120° sample. The increase in strength is attributed to second-phase precipitates, bimodal grain structure and high-density dislocations. ES-120° and ES-135° samples show less weakening of the basal texture in the edge zone than in the center zone. The ES-120° sample’s edge zone exhibited a fracture elongation of 18.2%. Excellent plasticity attributed to active slip system and bimodal grains. The microstructure results for the central and edge zones of the samples show that the shear angle leads to differences in the crystal orientation of the Mg alloys, and that different zones of the same sample also have different texture intensity due to the incorporation of ECAP. This study aims to reveal the deformation mechanism of Mg alloys in different shear angles and to provide a way to improve the plastic forming ability and comprehensive performance of Mg alloys.

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