Hot-press sintering of MA Fe-based nanocrystalline/amorphous
soft magnetic powder①
soft magnetic powder①
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Institute of Materials Science and Engineering, Tongji University, Shanghai 200092, China)
2. Institute of Materials Science and Engineering, Tongji University, Shanghai 200092, China)
Abstract: Microstructures and magnetic properties of Fe84Nb7B9, Fe80Ti8B12 and Fe32Ni36(Nb/V)7Si8B17 powders and their bulk alloys prepared by mechanical alloying(MA) method and hot-press sintering were studied. The results show that: 1) After MA for 20 h, nanocrystalline bcc single phase supersaturated solid solution forms in Fe84-Nb7B9and Fe80
Ti8B12alloys, amorphous structure forms in Fe32Ni36Nb7Si8B17 alloy, duplex microstructure composed of nanocrystalline γ-(FeNi) supersaturated solid solution and trace content of Fe2B phase forms in Fe32Ni36-V7Si8B17alloy. 2) The decomposition process of supersaturated solid solution phases in Fe84Nb7B9and Fe80Ti8B12alloys happens at 710-780℃, crystallization reaction in Fe32Ni36Nb7Si8B17alloy happens at 530℃(the temperature of peak value) and residual amorphous crystallized further happens at 760℃(the temperature of peak value), phase decomposition process of supersaturated solid solution at 780℃(the temperature of peak value) and crystallization reaction at 431℃(the temperature of peak value) happens in Fe32Ni36V7Si8B17 alloy. 3) under 900℃, 30 MPa, 0.5 h hot-press sintering conditions, bulk alloys with high relative density(94.7% 95.8%) can be obtained. Except that the grain size of Fe84Nb7B9 bulk alloy is large, superfine grains (grain size 50 200 nm) are obtained in other alloys. Except that single phase microstructure is obtained in Fe80Ti8B12 bulk alloy, multi-phase microstructures are obtained in other alloys. 4) The magnetic properties of Fe80Ti8B12 bulk alloy(Bs=1.74 T,Hc=4.35 kA/m) are significantly superior to those of other bulk alloys, which is related to the different phases of nanocrystalline or amorphous powder formed during hot-press sintering process and grain size.
Ti8B12alloys, amorphous structure forms in Fe32Ni36Nb7Si8B17 alloy, duplex microstructure composed of nanocrystalline γ-(FeNi) supersaturated solid solution and trace content of Fe2B phase forms in Fe32Ni36-V7Si8B17alloy. 2) The decomposition process of supersaturated solid solution phases in Fe84Nb7B9and Fe80Ti8B12alloys happens at 710-780℃, crystallization reaction in Fe32Ni36Nb7Si8B17alloy happens at 530℃(the temperature of peak value) and residual amorphous crystallized further happens at 760℃(the temperature of peak value), phase decomposition process of supersaturated solid solution at 780℃(the temperature of peak value) and crystallization reaction at 431℃(the temperature of peak value) happens in Fe32Ni36V7Si8B17 alloy. 3) under 900℃, 30 MPa, 0.5 h hot-press sintering conditions, bulk alloys with high relative density(94.7% 95.8%) can be obtained. Except that the grain size of Fe84Nb7B9 bulk alloy is large, superfine grains (grain size 50 200 nm) are obtained in other alloys. Except that single phase microstructure is obtained in Fe80Ti8B12 bulk alloy, multi-phase microstructures are obtained in other alloys. 4) The magnetic properties of Fe80Ti8B12 bulk alloy(Bs=1.74 T,Hc=4.35 kA/m) are significantly superior to those of other bulk alloys, which is related to the different phases of nanocrystalline or amorphous powder formed during hot-press sintering process and grain size.
Key words: Fe-based soft magnetic alloys; high energy milling; hot-press sintering; amorphous phase; magnetic properties