Effect of ECAP die angle on the strain homogeneity, microstructural evolution, crystallographic texture and mechanical properties of pure magnesium: numerical simulation and experimental approach

Billets of pure Mg were processed using two ECAP dies with internal channel angle of 90° and 120° for 4-passes of route Bc at 225 °C. Finite element analysis was used to investigate the deformation behavior of Mg billets. Electron back-scatter diffraction was utilized to analyze the microstructural evolution and the crystallographic texture of the ECAPed billets. Vicker's microhardness and the tensile properties were studied. The finite element simulations showed that the 90°-die revealed a relative more homogenous distribution of the plastic strain compared with the 120°-die. From EBSD analysis, 1-pass condition of the 90°-die showed a bimodal structure that consisted of newly formed fine grains and heavily distorted large ones, whereas 120°-die counterpart revealed fewer areas with fine-grained structure. Accumulating the plastic strain up to 4-passes in the 90°-die and 120°-die resulted in significant refining of 0.88 μm and 1.89 μm, respectively compared to the as-annealed counterpart of 6.34 μm. The texture after 1-Pass and 2-Passes showed weakening in its intensity, which resembles the B fiber texture of ideal orientation {0 0 0 1} <uvjw>. Increasing the number of ECAP passes to 4-passes resulted in a significant strong texture with more than 26 times random with the intense {0001} poles. This was attributed to the grain refining that occurred after 1-Pass and 2-Passes, which allowed the activation of more slip systems upon the 4-Passes. On the other hand, ECAP processing resulted in a significant increase in the tensile strength, hardness, and ductility.