In situ preparation of symmetrically graded microstructures by solidification in high-gradient magnetic field after melt and partial-melt processes

The effect of a symmetrically distributed magnetic-field gradient on the microstructure and magnetic properties of solidified and semi-solid isothermally annealed Mn-89.7 wt%Sb alloy was investigated experimentally. In the absence of an applied magnetic field, primary MnSb phases had a dendritic morphology after solidification. The content of primary MnSb-phase dendrites in the lower part of the sample decreased slightly with depth. After semi-solid isothermal annealing treatment, primary MnSb phase particles in the MnSb/Sb eutectic matrix were relatively evenly distributed along the vertical axis of the sample. The application of a symmetrical high magnetic-field gradient caused primary MnSb-phase dendrites and alloy particles to distribute along the middle of the sample with a symmetrical gradient. The content of primary MnSb-phase dendrites and particles first increased and then decreased along the vertical axis of the sample. The saturation magnetization of this alloy is related to its MnSb phase content. Therefore, the saturation magnetization of the Mne89.7 wt%Sb alloy samples that were solidified and semi-solidly isothermally annealed under a symmetrical magnetic-field gradient increased and then decreased along the vertical axis of the sample. This symmetrical distribution of the saturation magnetization intensity was caused by the magnetic force driving the Mn-enriched zone or MnSb particles towards the center of the specimen. (C) 2016 Elsevier B.V. All rights reserved.