Microstructural analysis and tensile properties of Mg-1.8Nd-0.4Zr-0.3Ca alloy processed by asymmetric upsetting shear extrusion

This study employs a novel processing technique known as Asymmetric Upsetting-Shear Extrusion (AUSE) to process an Mg-1.8Nd-0.4Zr-0.3Ca alloy. The effects of this asymmetric upsetting-shear deformation method on the microstructure of both the conical reduction zone and the formed material were systematically examined using electron backscatter diffraction (EBSD). Additionally, the tensile properties of the formed material were tested. The results revealed significant differences in grain refinement degree and texture intensity among the upper, middle, and lower regions of the conical reduction zone under AUSE deformation. In comparison, the upper region is characterized by the highest degree of grain refinement and the lowest texture intensity. This is primarily attributed to the heterogeneous strain distribution perpendicular to the extrusion direction within the conical reduction zone, resulting in differential strain storage across regions. This will lead to regional differences in the extent of both grain refinement and texture weakening within the conical reduction zone. Furthermore, AUSE process suppressed basal slip activity while enhancing non-basal slip systems, which contributes to improved material ductility. The grain size in the formed region was refined to approximately 1.25 μm. Remarkably, the microstructure in the formed region exhibited a heterogeneous grain structure, facilitating a balanced development of strength and ductility. Mechanical testing demonstrated that the material achieved an ultimate tensile strength (UTS) of 351.7 MPa and an elongation (EL) of 9.42 %. Examination of the tensile fracture morphology revealed that the fracture type is quasi-cleavage.