Crystallographic effect of a high magnetic field on a solidified hypoeutectic Zn–Al alloy

Hypoeutectic Zn-4.45 wt% Al solidified under a high magnetic field was investigated crystallographically. With the field, the primary zinc-rich beta phase is distributed homogeneously and orients with the c axis perpendicular to the magnetic field direction. These results are attributed to the magnetic viscosity resistance force and the magnetocrystalline anisotropy of zinc, respectively. The orientation modification also leads to a preferential alignment of the flat-shaped primary beta dendrites. Furthermore, with the field, the eutectic beta phase shows an orientation character similar to that of the primary beta phase. This arises from its continuous growth with the primary beta phase. In addition, a specific crystallographic orientation relationship (\0001\(beta)parallel to\111\(alpha), (beta)parallel to (alpha)) exists in some of the eutectics (between the eutectic zinc-rich beta and aluminium-rich alpha phases). However, this orientation relationship is related to the distribution of primary beta dendrites, which originates from the independent nucleation of the pseudo-primary alpha phase attached to the primary beta dendrites.