Effect of the growth velocity on microstructure, orientation, and magnetostriction in Fe₈₁Ga₁₉ alloy

Polycrystalline Fe₈₁Ga₁₉ rods were directionally solidified by an induction heating zone melting method at different growth velocities. The microstructure, preferred orientation, and magnetostriction were investigated. As the growth velocity increased, the solidification morphology transited from columnar to equiaxed. Simultaneously, the solid/liquid interface morphology evolved from planar to cellular, accompanied by an increase in the interface concave height. The 〈001〉 preferred orientation was detected along the axial direction of the grown rod at 10 mm/h. With the increased growth velocity, the 〈001〉 preferred orientation deviated from the axial direction, and the 〈001〉 orientation degree was weakened. The saturation magnetostriction of the grown rod was 305 ppm at 10 mm/h, but it deteriorated at higher velocities. The decreased magnetostriction was attributed to the microstructure transition and the weakened 〈001〉 preferred orientation.