A quantitative study on planar mechanical anisotropy of a Mg-2Zn-1Ca alloy

Abstract

A TD-tilted basal texture in Mg alloys often generates a strong planar mechanical anisotropy. Unfortunately, there has been not a quantitative study on this issue. In the present study, the mechanisms for the anisotropy of tensile yield strength in RD-TD plane were quantitatively studied for a Mg-2Zn-1Ca alloy with different grain sizes and textures. Here, RD and TD refer to the rolling direction and transverse direction of the plate. The results show that there is a strong planar yield anisotropy (∼24 ± 5 MPa), regardless of grain size, while this yield anisotropy is absent in texture with a circular distribution of basal poles. The examination of microstructure and X-ray diffraction analysis reveals that, beside basal slip as the predominant mode under both RD-tension and TD-tension, prismatic slip in RD-tension and both prismatic slip and extension twinning in TD-tension are also important. The parameters of Hall-Petch relation are also used to further analyze the mechanism for yield anisotropy. The changeable intercept, σ0, and invariant Hall-Petch slope, k, between RD-tension and TD-tension are rationalized accounting for this anisotropy. The reasons why there are different σ0 and similar k between TD-tension and RD-tension are quantitively discussed. At last, a texture design for decreasing the planar yield anisotropy is given.