Convergent 열처리를 통한 Nd23Dy10Fe64TM2B1 소결자석의 보자력 향상

Abstract

In this study, a convergent heat treatment was performed in certain temperature regions in order to control the microstructures of Nd-rich phases and to reduce thermal stress on grain boundaries which could be caused during expansion and shrinkage of Nd-rich and Nd2Fe14B phases. The difference of thermal expansion coefficient between Nd2Fe14B and Nd-rich phases is the mechanism for convergent heat treatment. The Nd-rich phases which were located in junctions could penetrate into the grain boundaries between Nd2Fe14B phases due to the difference of thermal expansion coefficient. Through the convergent heat treatment, the microcracks that were observed in cyclic heat treatment were not observed and coercivity was increased to 34.05 kOe at 8 cycles.