Microstructural evolution and mechanical properties of Mg–Cu–Zn ultrafine eutectic composites

Novel ultrafine eutectic composites containing structural and spatial heterogeneities have been systematically developed in an Mg–Cu–Zn ternary system. Microstructural investigations of the ultrafine eutectic composites revealed that the bimodal eutectic structure consists of a mixture of cellular-type fine (α-Mg + MgZn₂) and anomalous-type coarse (α-Mg + MgZn₂ + MgCuZn) eutectic structures. An Mg₇₂Cu₅Zn₂₃ alloy composed of the bimodal eutectic structure without micron-scale α-Mg dendrites presents a strong improvement of yield strength up to 455 MPa with a decent plastic strain of 5%. The rotation of the bimodal eutectic colony along the interfaces is considered to be an effective way to dissipate the stress localization thus enhancing the macroscopic plasticity.