Ductility enhancement in Mg-0.2%Ce alloys

Abstract

Ductility of Mg alloys can be enhanced by alloying, controlling the grain size and randomizing the texture. In this study, Mg-0.2%Ce alloys were processed using rolling, multi-axial forging (MAF) and equal channel angular pressing (ECAP) to fabricate three different textured samples from the same alloy. The samples were further annealed to produce similar grain size without altering texture. Rolled sample had a strong basal {0001} texture, the MAF sample developed a weak {011¯2¯} [2¯31¯2] texture component in addition to the basal texture and the ECAP sample exhibited a strong non-basal {1¯21¯3} [2¯111¯] texture component. The tensile properties, texture evolution and relative slip/twin activities in the samples were investigated experimentally and numerically. The tensile yield strength, ultimate strength and uniform elongation of the rolled, MAF and ECAP samples were 110MPa, 250MPa, 17%; 60MPa, 200MPa, 30% and 55MPa, 250MPa and 40%, respectively. The non-basal texture components in ECAP and MAF samples favored the formation of extension twins and pyr. <c+a> slip during tensile loading. Full field crystal plasticity finite element modelling (CPFEM) using the initial texture of the materials as input provided insights into the activation of different deformation modes and observed differences in hardening mechanisms as well as strain localization and premature failure of the rolled samples. CPFEM analysis confirms that Ce addition reduces the relative values of the critical resolved shear stress (CRSS) for the slip and twinning systems which, in turn, allows for texture modification during material fabrication. These, combined with the ability to control grain size in MgCe alloy with excess Ce, provide options for ductility enhancement in Mg alloys.