A crystallographic study on the growth of Laves phase MgZn₂ during the solidification process of Zn–Mg alloy under a high magnetic field

Abstract

To date, much work has been done to clarify the physical and chemical characters of the prototypical Laves phase MgZn₂. However, there are few studies aiming at its growth during the solidification process, especially under a high magnetic field (HMF). In this work, binary Zn-4.8 wt% Mg alloy was solidified under different uniform HMFs to investigate the growth of the MgZn₂ phase from a crystallographic point of view. The results show that a typical primary MgZn₂ crystal has an elongated hexagonal prism-like shape, which prefers growing along the <0001> direction and is bound by the $\{ 10\bar{1}0\}$ side facets, irrespective of whether the HMF is applied. Without the HMF, the morphology, size and distribution of the primary MgZn₂ crystals are varied in the specimen. When a sufficiently strong HMF is applied, the microstructure becomes homogeneous: All the primary MgZn₂ crystals are medium-sized and distributed uniformly throughout the specimen. Meanwhile, they align horizontally, i.e., with the long axis perpendicular to the HMF. A crystallographic analysis indicates that <0001> (i.e., c-axis) is the preferred magnetization direction of the primary MgZn₂ crystals that orients perpendicular to the HMF. In addition, the non-equilibrium eutectic MgZn₂ crystals exhibit the same preferred orientation feature as that of the primary ones.