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.

Bin Ma;Xiaoqian Bao;Aizhi Sun;Jiheng Li;Xuexu Gao

State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing 100083,China;Institute for Advanced Materials and Technology,University of Science and Technology Beijing,Beijing 100083,China

稀土学报（英文版）

[1]Bin Ma;Xiaoqian Bao;Aizhi Sun;Jiheng Li;Xuexu Gao-.Microstructure evolution and coercivity mechanism of hydrogenation-disproportionation-desorption-recombination(HDDR)treated Nd-Fe-B strip cast alloys)[J].稀土学报（英文版）,2022(05):792-799

NdH2+x,hereditarily

Microstructure,evolution,coercivity,mechanism,hydrogenation,disproportionation,desorption,recombination,HDDR,treated,strip,cast,alloys,In,this,paper,systematically,investigated,microstructure,by,transmission,electron,microscopy,TEM,three,dimensional,atom,probe,3DAP,analyses,rod,like,phases,diameters,are,embedded,into,matrix,which,leads,textured,grains,migration,from,rich,region,during,absorption,process,contributes,uniform,redistribution,after,treatment,single,domain,sizes,exhibits,relatively,that,arises,pinning,motion,weak,axis,orientation,results,lower,reverse,field,reduce,remanence,Moreover,direct,contact,Nd2Fe14B,high,concentration,ferromagnetic,elements,content,Co,boundary,layer,strong,magneto,static,coupling,effect,among,nano,sized,inside,makes,magnetization,reversal,easily,decreases

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