采用液态急冷法制备了高熵Fe25Co25Pt25B25合金,研究了其热处理前后的组织结构及磁性能.结果表明:Fe25Co25Pt25B25高熵合金具有较高的非晶形成能力,液态急冷合金形成了非晶态结构,表现出软磁特性.Fe25Co25Pt25B25高熵非晶合金热处理结晶化过程为:非晶相→非晶相+fcc-(Fe,Co)Pt相→非晶相+fcc-(Fe,Co)Pt+L10-(Fe,Co)Pt+(Fe,Co)2B相→非晶相+L10-(Fe,Co)Pt+(Fe,Co)2B相→L10-(Fe,Co)Pt+(Fe,Co)2B相.经843 K 热处理900 s后,Fe25Co25Pt25B25 合金形成了由有序面心四方结构的永磁L10-(Fe,Co)Pt相和软磁(Fe,Co)2B相组成的纳米复相组织,平均晶粒尺寸约为19 nm,表现出纳米复相永磁体特性,其矫顽力(iHc)、剩磁(Br)、剩磁比(Mr/Ms)和磁能积((BH)max)分别为946.8 kA·m-1、0.46 T、0.78和40.9 kJ·m-3.其超大iHc主要是高熵化使L10相的c/a增大导致磁晶各向异性增大的结果.
Structure and magnetic properties of Fe25Co25Pt25B25 high-entropy nanocomposite magnet
Fe25Co25Pt25B25 high-entropy alloy was prepared by melt spinning,and its structure and magnetic properties before and after annealing were investigated.The results show that the Fe25Co25Pt25B25 high-entropy alloy has high amorphous-forming ability,and the melt-spun alloy forms an amorphous structure,exhibiting soft magnetic characteristics.The phase transformations during the annealing crystallization process of the Fe25Co25Pt25B25 high-entropy amorphous alloy are as follows:amorphous→ amorphous+fcc-(Fe,Co)Pt →amorphous+fcc-(Fe,Co)Pt+L10+(Fe,Co)2B → amorphous+L10+(Fe,Co)2B → L10+(Fe,Co)2B.After annealing at 843 K for 900 s,the Fe25Co25Pt25B25 alloy forms a nanocomposite structure consisting of a hard magnetic ordered face-centered tetragonal L10-(Fe,Co)Pt phase and a soft magnet(Fe,Co)2B phase,with an average grain size of about 19 nm,it shows the characteristics of nanocomposite magnets,and the coercivity(iHc),the remanence magnetization(Br),the remanence ratio(Mr/Ms)and magnetic energy product((BH)max)are 946.8 kA·m-1,0.46 T,0.78 and 40.9 kJ/m3,respectively.The ultra large iHc is mainly due to that the high-entropy lattice distortion effect increases the c/a ratio of the L10 phase,resulting in an increase in magnetocrystalline anisotropy.
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