Professor Matianyu Ma's team at Xi'an Jiaotong University, through in-depth research on the microstructural evolution and demagnetization mechanism of Sm2Co17-type light rare earth permanent magnetic materials, identified a new 2:17R' phase formed by the aggregation of structural defects. This phase, detrimental to magnetic properties, is a key factor leading to coercivity and knee field lower than theoretical values. The team has developed a new method to improve the coercivity and knee field of 2:17-type samarium-cobalt permanent magnetic materials. The research findings have recently been published in the "Acta Materialia" journal.
Different from traditional isothermal aging and slow cooling processes, the team introduced an additional rapid heating and cooling pretreatment before isothermal aging treatment. By increasing point defects and simultaneously maintaining a high density of line defects, they effectively enhanced the nucleation rate of the 1:5H precipitation phase, which plays a critical role in coercivity, and accelerated the decomposition rate of structural defects during isothermal aging. Comparative results show that after subsequent full heat treatment, the 1:5H precipitation phase significantly increased, while the 2:17R' phase decreased noticeably. This led to an increase of nearly 20% in coercivity (Hcj) and over 30% in knee field (Hk), surpassing the comprehensive magnetic properties of commercially available magnetic materials with similar compositions.
It is known that Sm2Co17-type light rare earth permanent magnetic materials are the strongest high-temperature magnetic materials, and they are the preferred choice for new-generation magnetic drive systems in high-speed rail transportation and electric aircraft operating at temperatures exceeding 300°C. After over 40 years of development, the remanence (magnetic induction strength provided to the external environment after magnetization) of such materials has approached theoretical values. However, their coercivity and knee field (reflecting the resistance to demagnetization, with higher values indicating stronger resistance) remain far below theoretical values.
For more information, refer to the related paper: https://doi.org/10.1016/j.actamat.2024.119966
