Investigation of microstructure and strength of AZ80 magnesium alloy by ECAP and aging treatment

Abstract

Grain refinement by equal channel angular pressing (ECAP) and aging was combined to strengthen a wrought Mg alloy AZ80. The resulting mechanical properties and microstructure were examined by uniaxial tensile test, optical microscope (OM) and transmission electronic microscope (TEM). It is found that ECAP for 8 passes at 633 K followed by aging treatment at 423 K is the optimum condition to strengthen AZ80 alloy. Microstructure analysis reveals that many discontinuous precipitates appear at grain boundaries, accompanied by a few continuous precipitates in grain interior. The strengthening effect of this combination method is not quite remarkable in comparison with simple fine-grain strengthening by ECAP without aging, which is probably due to the contradiction between the low temperature required for grain refinement by ECAP and the high temperature needed for solid solution during ECAP.