Effect of different c/a ratio on the microstructure and mechanical properties in magnesium alloys processed by ECAP

Abstract

Three magnesium alloys, AE21, AE42 and LAE442, were prepared by ECAP employing 1–12 passes. The microstructure evolution during ECAP was systematically analyzed by EBSD. The AE21 and AE42 alloys show typical texture after ECAP with grains predominantly oriented with basal planes inclined by ∼55° from processing direction. This texture results from activation of basal slip during ECAP following the route BC. The LAE442 alloy showed different texture formation, which is fully explained by different c/a ratio and activation of non-basal slip. The differences in the microstructure evolution resulted in different performance in mechanical loading. In the present study a complex investigation of mechanical properties is performed using uni-axial tensile and compression deformation tests and also by Vickers indentation that simulates multi-axial deformation. Resulting microhardness evolution was therefore correlated to grain size according to Hall–Petch relation and to the evolution of dislocation density measured by positron annihilation spectroscopy. On the other hand, the yield stress in the tensile and compression uni-axial deformation tests was determined mainly by the texture. It was shown that by tailoring the c/a ratio the typical texture development could be effectively suppressed in magnesium alloys processed by ECAP and in such way the negative effect of texture on strength can be avoided.