Microstructural homogeneity, texture, tensile and shear behavior of AM60 magnesium alloy produced by extrusion and equal channel angular pressing

Equal channel angular pressing (ECAP) experiments with various pass numbers were conducted for the extruded AM60 magnesium alloy to investigate the influence of the operation on the microstructure and mechanical properties of the alloy. By this means, the grain structure of the material was refined from 19.2 μm to 2.3 μm after 6 passes at 220 °C. The shear punch testing (SPT) and uniaxial tensile tests were employed to evaluate the mechanical properties of the extruded and ECAPed samples. Both the yield stress (YS) and ultimate strength (US) obtained from the shear punch and tensile tests increased just after two passes but decreased with further pressing, though the grains became finer with increasing the pass number. The 6-pass ECAPed AM60 showed lower yield stress and higher ductility compared with the as-extruded material, indicating that texture softening overcame the strengthening effects of the grain refinement. The good correlation between the shear and tensile data obtained in the present investigation showed that SPT was a useful method for evaluation of the mechanical properties of the ECAPed fine-grained materials. The Vickers microhardness was also recorded on the polished cross sections of each sample and the results were plotted in the form of color-coded maps in order to provide a graphical presentation of the hardness distribution. It was found that the improvement in the homogeneity of hardness with a greater number of passes was due to a reasonably homogeneous microstructure throughout the product.

► All the tests showed the maximum strength for AM60 alloy just after the 2nd pass of ECAP.
► Texture softening reduced YS and UTS of AM60 after the 2nd pass of ECAP operation.
► The shear punch test can be employed instead of the tensile test for the Mg alloys.
► Tensile/shear data ratios were 1.70 and 1.83 for the yield and ultimate strengths of AM60.
► The greater the number of passes, the greater was the uniformity of the ECAPed bar.