B含量对Fe_(90-x)Pt_(10)B_(x)(x=15~40)液态急冷合金组织结构和磁性能的影响

Effects of B Content on Structure Evolution and Magnetic Properties of Melt-Spun Fe_(90-x)Pt_(10)B_(x)(x=15~40)Alloys

研究了低Pt含量的Fe_(90-x)Pt_(10)B_(x)(x=15~40,原子分数,%)系液态急冷合金热处理前后的组织结构和磁性能。结果表明,x由15增加至25~30可提高合金的非晶形成能力,急冷合金由非晶+fcc-FePt复相组织转变为单一非晶态结构;当x进一步增加至35和40时,合金分别由fcc-FePt+Fe_(2)B+FeB和L1_(0)-FePt+FeB纳米复相组织构成。经适当热处理后,x=15~20时的合金具有fcc-FePt+Fe_(2)B复相组织而呈软磁性;当x=25~40时的合金形成了由有序面心四方结构的永磁L1_(0)-FePt相和软磁Fe_(2)B/FeB组成的纳米复相组织,显示出永磁特性,其中x=30的合金经823 K热处理900 s后具有最佳的永磁性能,矫顽力、剩磁和最大磁能积分别为173.2 kA/m,1.20 T和88.3 kJ/m^(3),其优异的永磁性能源于分布均匀、平均晶粒尺寸约为15 nm的永磁L1_(0)-FePt相和软磁Fe_(2)B相间的交换耦合作用。

The structure evolution and magnetic properties of melt-spun Fe_(90-x)Pt_(10)B_(x)(x=15~40)alloys before and after annealing were investigated.The results show that the increase of x from 15 to 25~30 can improve the amorphous forming ability of the alloy,and the melt-spun structure transforms from a composite composed of amorphous and fcc-FePt phases to a single amorphous phase.Further increasing x to 35 and 40 results in the formation of fcc-FePt+Fe_(2)B+Fe B and L1_(0)-FePt+FeB phases,respectively.After appropriate annealing,dual phases of fcc-FePt+Fe_(2)B are formed for the alloys with x=15~20,which have soft magnetic properties,while the nanocomposite structure consisting of L1_(0)-FePt together with Fe_(2)B and/or Fe B phases is obtained for the alloys with x=25~40,which exhibit the characteristics of the nanocomposite magnets.The best permanent magnetic properties are obtained for the alloy with x=30 annealed at 823 K for 900 s,of which the coercivity,remanence and maximum energy product are 173.2 kA/m,1.20 T,and 88.3 kJ/m^(3),respectively.The good permanent magnetic performance is due to the formation of a more fine and homogeneous L10-FePt/Fe_(2)B nanocomposite structure with an average grain size of about 15 nm.