Microstructures and tensile properties of ECAE processed Mg-Al-Zn alloys

In this study, ECAE (equal-channel angular extrusion) processing was applied to Mg-Al-Zn alloys and subsequently secondary processing by hot rolling was carried out in order to investigate possible changes in properties of the ECAE processed alloys. In 4-pass ECAE processed specimens of a Mg-3%Al-3%Zn alloy, ductility improves remarkably compared to that of as-cast samples because the microstructures of the ECAE processed alloy have fine and equiaxed grains due to dynamic recrystallization during ECAE processing which was carried out at 523 K and because their basal plane orients towards 45° to the extrusion direction. On the other hand, many {101¯1} twins which cross at an angle of 60° to the rolling direction are observed in the microstructure of 4-pass-ECAE + rolled specimens. In this specimen, although the basal plane orients parallel to the rolled surface, tensile strength and 0.2% proof strength are improved significantly and good elongation is retained because twinning and basal slip in twins operate during tensile deformation. This result shows that ECAE processed materials exhibit good formability and it is possible to obtain superior mechanical properties by subjecting ECAE processed samples to secondary processing such as rolling and forging without heat treatment.