Textured structures of MnBi precipitated phase in Bi-Mn alloys solidified in a magnetic field

Magnetic textured structures of MnBi precipitated phase in Bi-6% Mn alloy were studied experimentally during solidification of the alloy from the semi solid zone below 446°C. An abrupt shape change of MnBi phase from regular hexagonal grains to oblate grains grown up along their ab-plane was observed firstly near 340°C, which is the transformation temperature of MnBi compound from paramagnetic state to ferromagnetic state. After the production of ferromagnetic MnBi grains from the magnetic transformation, the textured structures form by the rotation of the precipitated grains. The critical magnetic flux intensity for the textured structures decreases with increasing the heating temperature during solidification from the semi solid zone below 355°C and increases between 355°C and 446°C. Solidification from the semi solid zone below 355°C is propitious to fabricate hypereutectic Bi/MnBi magnetic composites with excellent properties.