Microstructure refinement and high-temperature tensile properties of Mg–12Gd–3Y–0.5Zr alloy after equal channel angular pressing

ABSTRACT Grain refinement is significant for the mechanical properties of engineering alloys. We achieved a bi-ultrafine microstructure in an Mg–12Gd–3Y–0.5Zr alloy through equal channel angular pressing (ECAP) at 300°C. The ECAP not only refined the matrix grains but also broke the large intermetallic particles into fine secondary particles and then rearranged them at the grain boundaries. These fine particles can suppress the growth of the recrystallised grains, as well as promote nucleation for recrystallisation. After four passes of ECAP, a uniform microstructure with both the matrix grain (∼500 nm) and the particle size (∼300 nm) in the ultrafine range was obtained. This unique microstructure resulted in a good combination of strength (>300MPa) and elongation to failure (>35%) at 200°C, which sheds new light on refining microstructure to obtain good mechanical performance at elevated temperatures for Mg alloys.