Growth behavior of Zn-rich phase in Zn-Mg alloy under a high magnetic field

Abstract

In Zn-based alloys, Zn-rich phase is generally one of the most important structural components formed during the solidification process. However, little work has been done to investigate and control particularly the growth behavior of Zn-rich phase, which usually plays an important role in determining the structures and the final properties of the alloys. Based on this, Zn-Mg alloy was solidified under different high magnetic fields (HMFs) in this work. The results show that, irrespective of whether the HMFs are imposed or not, the primary Zn-rich crystals prefer growing along 101¯0 in the {0001} basal plane and along 〈0001〉 in the {1¯21¯0} plane, and finally form less- or well-developed dendrites with strong morphological anisotropy in three dimensions. Due to the magnetocrystalline anisotropy, however, the HMFs tend to orient the primary Zn-rich crystals preferentially with the c-axis perpendicular to the HMFs direction (i.e., tend to produce {0001} basal texture) and thus to align them with the longer axes parallel to the HMFs direction. The eutectic Zn-rich crystals follow the orientations of their adjacent primary crystals and then also develop {0001} basal texture under a high magnetic field. In addition, correlated with the orientations and the anisotropic morphology, the primary Zn-rich crystals exhibit various two-dimensional shapes in the longitudinal and transverse sections of the specimens.