Microstructures of Fe2RE (RE; Tb and Nd) alloys produced by drop tube processing

Fe2Tb, Fe2Nd, and Fe2(Tb0.5Nd0.5) alloy samples were melted and then solidified in the containerless state of a drop tube. In the Fe2Tb samples, the Laves phase was directly formed from the melt during its free fall. The amount of the Laves phase increased as the sample diameter decreased. On the other hand, in the Fe2Nd sample, the Nd2Fe17 and intergranular Nd phases were formed regardless of the sample diameter. In the Fe2(Tb0.5Nd0.5) sample contained the Laves phase that was formed via a peritectic reaction between the Fe3RE and liquid phases. The Fe3RE phase, the ratio of Nd to Tb was 0.59:0.41, was also directly formed from the undercooled melt, when the sample diameter was below 800 μm.