Microstructure evolution and coercivity mechanism of hydrogenation-disproportionation-desorption-recombination(HDDR)treated Nd-Fe-B strip cast alloys

• 作者: Bin Ma Xiaoqian Bao Aizhi Sun Jiheng Li Xuexu Gao
• 来源期刊: 稀土学报（英文版）
• 年，卷（期）: 2022,（5）
• 所属期刊栏目: MAGNETISM AND MAGNETIC MATERIALS
• 页码范围: 792-799
• 页数: 8页
• 语种: 英文

摘要

In this paper,we systematically investigated the microstructure evolution and coercivity mechanism of hydrogenation-disproportionation-desorption-recombination(HDDR)treated Nd-Fe-B strip cast alloys by transmission electron microscopy(TEM)and three-dimensional atom probe(3DAP)analyses.The rod-like NdH2+x phases with diameters of 10-20 nm are embedded into α-Fe matrix,which hereditarily leads to textured grains in HDDR alloy.The migration of NdH2+x from Nd-rich region to α-Fe matrix during hydrogen absorption process contributes to the uniform redistribution of Nd-rich phases after HDDR treatment.The HDDR alloy with single domain grain sizes of 200-300 nm exhibits relatively low coercivity of 1.01 T that arises from pinning magnetic domain motion.The weak c-axis orientation of HDDR alloy results in a lower reverse magnetic field(coercivity)to reduce remanence to 0.Moreover,the direct contact of Nd2Fe14B grains and the high concentration of ferromagnetic elements(Fe content ≈ 66.06 at％,Co content ≈ 0.91 at％)in Nd-rich grain boundary layer lead to strong magneto-static coupling effect among Nd2Fe14B grains.The nano-sized α-Fe inside Nd2Fe14B matrix makes the magnetization reversal easily and decreases the coercivity of HDDR alloy.