Managing strength and ductility in AZ91 magnesium alloy through ECAP combined with prior and post aging treatment

In the present work, we firstly and comparatively investigated the microstructure evolution and mechanical properties of AZ91 alloy processed by equal channel angular pressing (ECAP) combined with prior and post aging treatment. Both processes induce homogenous microstructures consisting of fine grains modified by uniformly dispersed spherical precipitates. The prior aging treatment facilitates a well-developed dynamic re-crystallized microstructure with low dislocation density, and finer and more precipitates, while both processes induce comparable grain size. Thus, the prior aging treatment benefits to the occurrence of dynamic re-crystallization during subsequent ECAP processing. Furthermore, both the strength and ductility of AZ91 alloy are enhanced and flexibly managed through ECAP with a combination of prior or post aging treatment. The post aging treatment is of benefit to the improvement in yield strength, while the prior aging treatment facilitates the more significant ductility enhancement.