Direct Crystallization of the Nd₂Fe₁₄B Peritectic Phase by Containerless Solidification in a Drop Tube

抄録

Nd₂Fe₁₄B molten alloy droplets were containerlessly solidified using a 25 m drop tube. The relationship between the sample diameter and the microstructure was investigated. The diameter of the resultant spherical samples was in range of 150 to 2000 μm. When sample diameter was larger than 500 μm, the microstructure of the spherical sample consisted of the α-Fe phase embedded in matrix of the Nd₂Fe₁₄B phase within entire sections. In the spherical sample with diameter of 400 μm, the microstructures consisted of two regions, one was columnar grains of the Nd₂Fe₁₄B phase and the other was α-Fe phase embedded in matrix of the Nd₂Fe₁₄B phase. The columnar Nd₂Fe₁₄B region expanded as the sample diameter decreased from 400 to 350 μm. When sample diameter reduced to 250 μm, the microstructure of a spherical sample consisted of the pure dendritic Nd₂Fe₁₄B phase without any α-Fe phase.