A multi-angular extrusion process for fine-grain magnesium alloy plate

The precise forming process with fine-grain strengthening method of magnesium alloy is a common technical problem that needs to be urgently addressed for lightweight application. In this paper, a multi-angular extrusion process integrating severe plastic deformation (SPD) technique and hot forming process was proposed to manufacture the fine-grain plate of AZ80 magnesium alloy. Shear deformation path was introduced via the variable section and secondary angle of mold cavity. The unified internal state variable (ISV) based finite element (FE) model was established to simulate the multi-angular extrusion process. The interaction of viscoplastic flow and microstructure evolution was embedded into the user defined subroutine of DEFORM-3D software. The inhomogeneous strain distribution and microstructure characteristics during the extrusion process were investigated. The improvement of fine-grain homogeneity via the two-pass angular shear deformation was revealed. A fine-grain magnesium alloy plate with good forming performance and average grain size of 9 mu m was manufactured. The yield strength is increased to 259 MPa by 23.3 %, ultimate tensile strength is increased to 338 MPa by 27.5 %, and elongation is increased to 12.9 % by 122.4 %. The developed multi-angular extrusion process can be applied to the integrated manufacturing of shape and performance of fine-grain Mg components.