Improvement of bending strength via regenerated interstitial phase at the triple junction phase on sintered Nd–Fe–B alloy

Abstract

Understanding the mechanical properties of sintered Nd-Fe-B magnets is critical for improving the rate of finished products in grinding and cutting. During the preparation of sintered Nd-Fe-B magnet, carbon elements inevitably remain in the magnet. In this paper, the effect of carbon on the bending strength of sintered Nd-Fe-B was investigated and the fracture mechanism was analyzed. In the case of the sample having a high carbon content, the bending strength was significantly increased. Observation of the microstructure shows that the carbon content does not affect the grain size of the main phase. Stress concentration is applied by pre-cracking. It is directly observed that the sintered Nd-Fe-B crack source is located at the triple junction phase (TJP). It was found that almost all the carbon elements were concentrated in the TJP using electron probe microanalyzer (EPMA). At the same time, the formation of neodymium carbide contributes to strengthening TJP, which improves the difficulty of crack nucleation and the resistance of crack propagation.