ECAP effect on the micro-structure and mechanical properties of AM30 magnesium alloy

The effect of Equal Channel Angular Pressing (ECAP) process on the microstructure and mechanical properties of wrought AM30 magnesium alloy was studied. Rod-shaped samples with 19 mm diameter were machined from an extrusion piece in the extrusion direction. Samples were pressed using an isothermal conical split ECAP die, with an internal channel angle of 90°and outer radius angle of 20° at 275 °C. The process was performed up to 4 passes, with samples being rotated by 90° in the same orientation between passes. ECAP samples were sectioned for micro structural studies and tested for mechanical properties. The results showed a considerable effect of ECAP process in creating an ultrafine grain size structure. The grain structure was refined from original size 20.4 µm to 3.9 µm through the four passes. The grain uniformity increased as the number of passes increased, which was also reflected in the measured microhardness distribution color-coded maps. The elongation was increased in almost all passes, but the tensile yield strength reduction was observed. The changes in mechanical behaviors were due to texture modification. The twining was found in the compression test. The comparison of tensile and the compression test results along the ECAP direction showed that asymmetry in yield were reduced as the number of passes increased.