Equal-channel angular pressing of magnesium alloy AZ91 and its effects on microstructure and mechanical properties

Equal-channel angular pressing (ECAP) experiments were conducted on a hot-rolled AZ91 magnesium alloy to investigate their influence on its microstructure and mechanical properties. Homogeneously refined grains with a size of about 2 μm are observed after two-step ECAP processing. During ECAP, many fine Mg17Al12 phases precipitate at grain boundaries. The yield strength, ultimate tensile strength and elongation of AZ91 remarkably increase, respectively, to 290, 417 MPa and 8.45% after two-step ECAP with four passes at 225 °C and two passes at 180 °C. The high strength of the ECAP-processed alloy is due to grain refinement and to the precipitation of Mg17Al12 phase during ECAP. It is also shown that the morphology of the Mg17Al12 strongly influences the mechanical behavior of the ECAP-processed alloy.