Development of nanocrystalline soft magnetic alloy with high saturation magnetic induction produced in air

点击翻译按钮获取中文摘要

The nanocrystalline soft magnetic Fe-Nb-B based alloys, which can be produced by melt-spinning in air, with high saturation magnetic induction (B_s) as well as good soft magnetic properties have been developed. The Fe_<84>Nb_7B_9 alloy, which is the typical composition of the ternary Fe-Nb-B alloys, produced in air was extremely oxidized and showed brittleness. The ductile ribbons with the metallic luster were obtained for the ternary alloys with 6 at% Nb or less. Furthermore, higher B_s than 1.6 T has been obtained for the alloys with 6 at% Nb or less. However, the alloys exhibit inferior soft magnetic properties because the alloys have a mixed as-quenched structure composed of an amorphous phase and coarse α-Fe grains. These grains remain in the nanostructure after the crystallization and deteriorate the soft magnetic properties.The effect of the addition of some elements to Fe-Nb-B alloys on the as-quenched structure and the soft magnetic properties in the nanocrystallized state has been investigated. The simultaneous replacement of B by 1 at% P and Fe by 0.1 at% Cu in the alloy decreases the α-Fe grain size to the nano-scale in an as-quenched state and leads to a homogeneous nanostructure with good soft magnetic properties after crystallization. Analysis based on the random anisotropy model shows that a homogeneous nanostructure with small volume fraction of an inter-granular amorphous phase which has high Curie temperature is necessary for realizing the good soft magnetic properties. The Fe_<84.9>Nb_6B_8P_1Cu_<0.1> alloy exhibits high permeability of 41,000 at 1 kHz, very low core loss of 0.11 W/kg at 1.4 T and 50 Hz as well as higher B_S of about 1.61 T than that of the Fe_<84>Nb_7B_9 alloy.