Presentation Information
[P1-33]Study of microstresses in sintered NdFeB magnets and their effects on magnetic properties
*Shengen Guan1, Zihao Wang1, Ning Wang1, Zhaohong Feng1, Xuexu Gao1, Jiheng Li1, Zhimeng Guo1, Xiaoqian Bao1 (1. University of Science and Technology Beijing (China))
Keywords:
Sintered NdFeB magnets,Coercivity,Microstresses
Sintered NdFeB magnets are widely used in high-performance electric motors, consumer electronic devices, and other applications due to their excellent magnetic properties. However, the current commercial NdFeB magnets still have relatively low coercivity (~ 1.2 T), which is less than 20% of the Stoner-Wolfarth limit (around 7 T) predicted in the ideal model, i.e., the “Brown paradox” of NdFeB magnets. It is important to reveal the intrinsic mechanism of the decrease in coercivity of NdFeB magnets to further enhance their magnetic properties.
We consider that the differences in lattice constants and thermal expansion coefficients between the 2:14:1 phase and the grain boundary phase in NdFeB magnets may lead to the generation of microstresses with different magnitudes and distributions inside the magnets. Furthermore, we speculate that the microstresses have an important effect on the magnetic properties (remanent magnetization, coercivity) of the magnets and verified it. In this work, we systematically characterized the microstresses inside sintered NdFeB magnets using in-situ XRD, HRTEM, and geometrical phase analysis (GPA). The magnitude, distribution, and direction of the microstresses are explored, and the effects of the microstresses on the remanent magnetization and coercivity of sintered NdFeB magnets are discussed. Our study shows that the microstresses in NdFeB magnets are closely related to the cooling rate, the microstructure of grain boundary phase, and the orientation of 2:14:1 grain. The generation of microstresses is one of the reasons for the decrease in the coercivity of NdFeB magnets. This work reveals the origin of the loss of magnetic properties and provides guidance for the further development of high-performance sintered NdFeB magnets.
We consider that the differences in lattice constants and thermal expansion coefficients between the 2:14:1 phase and the grain boundary phase in NdFeB magnets may lead to the generation of microstresses with different magnitudes and distributions inside the magnets. Furthermore, we speculate that the microstresses have an important effect on the magnetic properties (remanent magnetization, coercivity) of the magnets and verified it. In this work, we systematically characterized the microstresses inside sintered NdFeB magnets using in-situ XRD, HRTEM, and geometrical phase analysis (GPA). The magnitude, distribution, and direction of the microstresses are explored, and the effects of the microstresses on the remanent magnetization and coercivity of sintered NdFeB magnets are discussed. Our study shows that the microstresses in NdFeB magnets are closely related to the cooling rate, the microstructure of grain boundary phase, and the orientation of 2:14:1 grain. The generation of microstresses is one of the reasons for the decrease in the coercivity of NdFeB magnets. This work reveals the origin of the loss of magnetic properties and provides guidance for the further development of high-performance sintered NdFeB magnets.