A microstructural and crystallographic investigation of the precipitation behaviour of a primary Al₃Zr phase under a high magnetic field

Abstract

The effects of a high magnetic field on the precipitation behaviour of the primary Al3Zr phase are investigated. With and without the field, the primary Al3Zr crystals possess three morphologies – small tabular crystals in the deposit layer, long bars and dendritic crystals. The dendritic crystals are probably those surviving from the initial material. The tabular crystals in the deposit layer are those surviving from the heating stage, whereas the long bars are those formed during cooling. With the field, the tabular crystals in the deposit layer and the long bars tend to orient with the 〈110〉 direction parallel to the field direction, but the orientation of the dendritic crystals is less affected. The orientation of the crystals in the deposit layer arises from their magnetocrystalline anisotropy, but that of the long bars and dendritic crystals is disturbed by gravity and the formation of compound twins, respectively. Increased Zr content raises the precipitation amount of the primary Al3Zr crystals but weakens the alignment tendency of the tabular ones in the deposit layer. The weakness of the alignment arises from interaction between the crystals.

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

“…where the subscript i denotes the crystallographic direction i, is the magnetic susceptibility, 0 the permeability in vacuum, V the volume of the crystal and N the demagnetization factor [here it should be specially mentioned that in weak magnetic materials the shape, i.e. N, has a negligible effect on the magnetization energy and thus the orientation of the crystals, as discussed in a prior work (Li et al, 2013)]. According to Jules (1949), the magnetic susceptibilities of zinc are jj = À0.169 Â 10 À6 (along the c axis) and ?…”

“…Therefore, a solidification microstructure study based on crystallography may effectively help discover and explain more phenomena induced by the magnetic field. So far, some information in some off-eutectic alloys under high magnetic field has been found crystallographically, such as the preferred magnetic field direction (FD) of primary crystals (Li et al, 2012(Li et al, , 2013. However, few researchers are involved in analysing the effect of a high magnetic field on the crystallographic growth features of primary crystals and eutectics, or the crystallographic orientation relationship (OR) between primary crystals and eutectics and between two eutectic phases.…”

Morphological and Crystallographic Characterization of Primary Zinc-Rich Crystals in a Ternary Sn-Zn-Bi Alloy under a High Magnetic Field

“…Crystals 2017, 7, 204 2 of 10 (usually negligible in conventional magnetic fields), thereby imposing more abundant effects on the structures of the alloys [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. It has been found that the HMFs could orient and align the structures [13][14][15][16][17], increase the phase transformation temperature [19], enhance the magnetic coercivities [16], suppress the diffusion of solute elements [21], modify the orientation relationship between the eutectics [22], and change the solid-liquid interface morphologies [23]. Hexagonal close-packed zinc is characterized by large solid-liquid interfacial energy anisotropy [24,25] and magnetocrystalline anisotropy [13,14].…”

“…To minimize the magnetization energy, the c-axis of the primary zinc-rich crystals tends to be rotated to the direction perpendicular to B under the HMFs. The driving force to start the rotation is the magnetic torque, as analysed in detail elsewhere [17,18,30]. However, to complete this rotation, a weak constraint medium is indispensable for the crystals [28].…”

Investigation on Reaction Interface between the Aluminum and K2ZrF6 by Freezing the Molten Salt Reaction

“…It is known that the qualities of the master alloys mainly refer to the size, morphology and distribution of the Al 3 Zr particle, which are closely related to the reaction and solidification conditions. Therefore, numerous studies have been carried out to investigate the above-mentioned aspects under different reaction and solidification conditions [2][3][4][5][6][7][8][9][10][11][12][13][14]. Lee and Terry [2], Zhao et al [8] and Li et al [14] found different types of Al 3 Zr particle with the ''blocky,'' ''needle-like'' and ''globular'' morphologies in the aluminum matrix.…”