Presentation Information
[P2-54]Temperature-Mediated In Situ Synthesis of Γ-FeZn Phase and Its Coercivity Enhancement Mechanism in Sm-Fe-N Magnets
*Dongsheng Shi1, Jingwu Zheng1, Wei Cai1, Liang Qiao1, Yao Ying1, Shenglei Che1 (1. Research Center of Magnetic and Electronic Materials, College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310014, China (China))
Keywords:
Sm-Fe-N/Zn magnet,Γ-FeZn phase,Coercivity,Heat treatment,Zn coating,Microstructure
The precise control of the Γ-FeZn phase is crucial for enhancing the coercivity of Sm-Fe-N/Zn magnets. In this study, low-coercivity Sm-Fe-N powder is used as raw material, and a uniform Zn layer is coated on the powder surface via electrodeposition. Combined with hot-pressing and heat treatment, the formation and distribution of the Γ-FeZn phase in Sm-Fe-N/Zn magnet is precisely regulated to significantly enhance the coercivity of the magnets. Furthermore, the microscopic mechanism and structure-property relationship are systematically revealed. The experimental results show that the coercivity of the magnets exhibits a non-monotonic trend of "decrease-sharp increase-decrease" within the heat treatment temperature range of 300-450°C. Notably, after heat treatment at 430°C, the coercivity reaches 14.605 kOe, representing a 2.56-fold increase compared to the initial value (5.698 kOe). Transmission electron microscopy (TEM) reveals the temperature-dependent evolution of the Γ-FeZn phase and its regulation mechanism on coercivity. Specifically, when the temperature is below the melting point of Zn, incomplete formation of the Γ-FeZn phase due to limited solid-state diffusion results in residual unreacted Zn and α-Fe on the powder surface, leading to reduced coercivity. when the temperature approaches the melting point of Zn, the enhanced fluidity of molten Zn promotes the reduction reaction, forming a continuous and dense Γ-FeZn coating layer, which significantly improves coercivity. However, further increasing the temperature causes excessive Zn diffusion, resulting in an overly thick Sm-Fe(Zn)-N interlayer and a subsequent decline in coercivity. This study provides new insights into the preparation and performance optimization of Sm-Fe-N/Zn magnets, while offering important theoretical and practical guidance for the precise control of the Γ-FeZn phase.
