Defects of (Tb0.3Dy0.7)Fe1.95 alloys with "one-step" directional solidification process

The main types of defect in the (Tb0.3Dy0.7)Fe-1.95 alloys with the "one-step" directional solidification process were investigated. The effect of the dendrite, grain boundaries, twin boundaries, and REFe3 precipitates on the magnetostrictive response of the (Tb0.3Dy0.7)Fe-1.95 alloys was analyzed respectively. The experiment results demonstrate that the dendrite, twin boundaries, and REFe3 precipitates can be avoided by modifying alloying ingredient, solidification parameters and annealing technique. The dendritic growth front often leads to dendrite sheet, rare earth-rich phase, and twin boundaries. The lower proportion of rare earth, or slow solidification rate, results in the occurrence of REFe3 precipitatates. It is vital for diminishing the defects to control the undercooling of solid-liquid interface at (2.4 similar to 5.1) x 10(4) K(.)s(.)cm(-2) so that the crystal grows in cellular growth front.