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 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 (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.