High ductility induced by un-DRXed grains in a Mg-Zn-Mn-La-Ce alloy

An approach of achieving high ductility as well as respectable high strength for low-Zn-containing wrought Mg alloy is presented in this paper. A low-cost and industry-compatible Mg-2Zn-0.3Mn-0.2La-0.1Ce alloy with highest yield strength (YS) of 289MPa, ultimate tensile strength (UTS) of 300MPa and excellent elongation (EL) of 32.7% is developed by traditional indirect extrusion. The microstructure and macro-textures of this alloy under various extrusion temperatures are characterized by OM, EBSD and XRD analysis. High quantity of dispersed elongated un-DRXed grains with various orientations form at relatively low extrusion temperatures, and many of them possess high basal Schmidt Factors (SFs) toward transverse directions. TEM analysis reveals a large number of networked dislocations passing through the deformation bands along transverse directions within the un-DRXed grains, which suggests the integral deformation (bending) is achievable by dislocation motion. It is believed that the high ductility along extrusion direction is induced by the bendable elongated un-DRXed grains during tensile deformation by embodying the easy-to-failure regions, preventing the subsequent generation of micro-cracks and accommodating the stress concentration.