Rapid Solidification from Undercooled Melt of Fe-Rare Earth Magnetostriction Alloys

Abstract

Fe67(Nd33-xDyx), Fe67(Nd33-xTbx) (x= 0, 16.5, and 33) droplets were containerlessly solidified using a 26 m drop tube. This was a challenge to produce the Laves phase directly from the undercooled liquid, which have been theoretically predicted to exhibit the high magnetostrictive strain. In the Fe67Nd33 sample, the Nd2Fe17 and intergranular Nd phases were formed regardless of the sample diameter. On the other hand, in the Fe67Dy33 and Fe677Tb33 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. As a result, the Fe67Dy33 sample with a diameter of 430 μm only consisted of the Laves phase. The Fe67(Nd16.5Dy16.5) and Fe67(Nd16.5Tb16.5) samples contained the Laves phase that was formed via a peritectic reaction between the Fe3RE and liquid phases. The Fe3RE phase was also directly formed from the undercooled melt, when the sample diameter was below 800 μm.