Effect Of Annealing Temperature And P Element On The Structure And Magnetic Properties Of FeCo-based Nanocrystalline Alloys

Nanocrystalline alloy are widely used in various fields because of their excellent soft magnetic properties,such as transformers,chokes,etc.This article will mainly focus on the effect of annealing temperature on the high-temperature soft magnetic properties of(Fe_0.9Co_0.1)_72.7Al_0.8Si_13.5Cu₁Nb₃B₈V₁ alloy as well as the effect of P element addition on the crystallization mechanism,microstructure,and soft magnetic properties of(Fe_0.9Co_0.1)_73.5Si_13.5Nb₃Cu₁B_9-xP_x（x=0,2,4）alloys.The structure and soft magnetic properties of nanocrystalline(Fe_0.9Co_0.1)_72.7Al_0.8Si_13.5Cu₁Nb₃B₈V₁ alloy annealed at 510-690℃ were investigated by XRD patterns and temperature dependence of initial permeability.It was observed that when annealing temperature is in the ranges of 510-630℃,only soft magnetic crystalline phase precipitated from the amorphous matrix.With the increase of annealing temperature,the grain size（D）and volume fraction of crystalline phase(V_cry)both gradually increase from 11.9nm to 13.7nm and from 58%to 89%respectively,and the thickness of the amorphous layer（Λ）gradually decreases from2.37nm to 0.54nm.The change of initial permeability with temperature（μ_i-T curves）showed that theμ_i declines with temperature increasing,but the rate of descent is different,the higher annealing temperature（T_a）corresponds to the slower attenuation ofμ_i.The high-temperatureμ_i gradually improves with annealing temperature（T_a）increasing up to 630℃,and the higherμ_i of 1500 can be held up to 600℃.However,high temperatureμ_i dramatically deteriorates after annealing at 690℃ because of precipitating the hard magnetic phase from the residual amorphous matrix.It was also found that the initial permeability of 630℃-annealed(Fe_0.9Co_0.1)_72.7Al_0.8Si_13.5Cu₁Nb₃B₈V₁ alloy is greater than that of 560℃-annealed(Fe_0.5Co_0.5)_73.5Cu₁Nb₃Si_13.5B₉ alloy in the range of 400-600℃.Therefore,the high-temperature magnetic softness of(Fe_0.9Co_0.1)_72.7Al_0.8Si_13.5Cu₁Nb₃B₈V₁ alloy is better than that of(Fe_0.5Co_0.5)_73.5Cu₁Nb₃Si_13.5B₉ alloy.The effect of P element addition on the crystallization mechanism,microstructure,and soft magnetic properties of(Fe_0.9Co_0.1)_73.5Si_13.5Nb₃Cu₁B_9-xP_x（x=0,2.0,4.0）alloy were investigated.Through DSC analysis,it is found that with the addition of P,the first crystallization temperature gradually decreases,which is conducive to the precipitation of the soft magnetic crystallization phase at a lower temperature.However,for the alloy with x=4.0,the second crystallization temperature is lower and the crystallization temperature interval is smaller.It is not conducive to the formation of a single soft magnetic crystalline phase in a wide temperature range.At the same time,with the addition of the P element,the Curie temperature of the amorphous phase is gradually decreasing,and the high-temperature soft magnetic properties of the alloy with x=4.0 are poor.By studying the change of initial permeability with temperature after vacuum annealing,we found that the room temperature and high temperature soft magnetic properties of x=2.0 alloy are better than those of x=4.0 alloy.The excessive addition of P will destroy the soft magnetic properties of the alloy.So we further studied the soft magnetic properties of x=2.0alloy and observed that the 580℃-annealed(Fe_0.9Co_0.1)_73.5Si_13.5Nb₃Cu₁B₇P₂ alloy has the improved high temperature soft magnetic properties which is due to the thinner intercrystalline amorphous layer thickness.