Undercooling and solidification behavior of magnetostrictive Fe-20 at. pct Ga alloys

Using electromagnetic levitation melting combining fluxing method, the Fe-20 at. pct Ga alloy was undercooled through heating-cooling cycles. The samples, after recalescence, cooled down to about 1173 K, and then quenched into ice-water mixtures to maintain the microstructure of rapid solidification. A maximum bulk undercooling of 337 K was achieved. Within the undercooling range of 0-337 K, the microstructure evolution of bulk undercooled Fe-20 at. pct Ga was investigated. Over the whole range of undercooling, the solidification microstructures were equiaxed grains. When the undercooling was less than 221 K, the grain size decreased smoothly with increasing undercooling and had homogeneous distribution. When the undercooling reached the range of 230-315 K, the fine equiaxed grains and abnormal large grains coexisted, and the area fraction of abnormal large grains increased with increasing undercooling. When the undercooling exceeded 320 K, only large grains existed. Especially, when the undercooling was in the range of 173-221 K, the grain had preferred orientation. The Fe-20 at. pct Ga alloy rods with [0 0 1] preferred orientation was prepared by exciting the undercooled Fe-20 at. pct Ga melt at undercooling 205 K and the [001] preferred orientation was approximately 11.42 deg away from the rod axis.