Combined Effects of Anisotropy and Tension-Compression Asymmetry on the Torsional Response of AZ31 Mg

In this paper, it is demonstrated that only by accounting for the combined effects of anisotropy and tension-compression asymmetry it is possible to explain and accurately predict the peculiarities of the torsional response of a strongly textured AZ31 Mg material. To this end, an elastic-plastic model with yielding described by the anisotropic criterion of Cazacu et al. (2006) is used. It is shown that unlike Hill (1948) this model quantitatively predicts the experimental trends, namely that a specimen with its axial direction parallel with the normal direction elongates axially while a specimen with its axial direction along the rolling direction contracts axially. Moreover, using a self-consistent polycrystal model it is shown that the observed experimental axial effects can be predicted only if both slip and twinning are considered active, the level of accuracy being similar to that of Cazacu et al (2006) criterion. However, if it is assumed that the plastic deformation is fully accommodated by crystallographic slip, the predicted trends are similar to these according to Hill (1948) i.e. Swift effects are not captured in the normal direction while in the rolling direction they are also underestimated.

Keywords: Elastic-Plastic Model; anisotropy; twinning, axial effects, self-consistent viscoplastic modeling, Magnesium Alloys, strength differential effect.