Preparation of Ultra-Fine-Grained Mg-2.5Zn-1Ca Magnesium Alloy and Its Microstructure and Properties

An ultra-fine-grained Mg-2.5Zn-1Ca alloy was prepared by extrusion + equal channel angular extrusion ( ECAP) composite processing technology. The microstructure evolution characteristics during the deformation process were analyzed by OM, SEM, XRD, EBSD, etc. Combined with mechanics performance changes, strengthening mechanism of alloy during deformation was studied. The results show that after extrusion + ECAP deformation, the grains and the second phase grains are significantly refined, and the uniform fine grain structure is obtained after extrusion + 2 passes ECAP, with an average grain size of about 1.1 mu m; At the same time, the fine Ca2Mg6Zn3 particles are dispersed distributed in the matrix. The grain refinement is the result of the combined effect of severe plastic deformation, dynamic recrystallization, and the finely dispersed Ca2Mg6Zn3 phases. ECAP deformation significantly improves the mechanical properties of the alloy. The alloy after two passes ECAP has the highest tensile strength and elongation, which are 275 MPa and 17%, respectively. With the increase of ECAP deformation passes, the texture strength gradually weakens, and the basal texture gradually changes into a new texture. Moreover, ECAP deformation alloy has higher non-basal Schmid factor, and the microstructure is uniformly refined, which makes the material have better elongation.