摘要
To investigate the coercivity,corrosion resistance,and thermal stability of Nd-Fe-B magnets,their properties were investigated at room and high temperature before and after doping with Dy（80）Ga（20）（at.%） powder.The coercivity of the magnets increased from the undoped value of 12.72 kOe to a doped value of 21.44 kOe.A micro-structural analysis indicates that a well-developed core-shell structure forms in the magnets doped with Dy（80）Ga（20） powder.The improvement in magnetic properties is believed to be related to the refined and uniform matrix grains,continuous grain boundaries,and a hardened（Nd,Dy）2Fe（14）B shell surrounding the matrix grains.Additionally,the doped magnets exhibit an obvious improvement in thermal stability.For the magnets with added Dy（80）Ga（20） powder,the temperature coefficients of remanence（α） and coercivity（β） increased to-0.106%℃-（-1） and-0.60%℃-（-1） over the range 20-100 ℃,compared to temperature coefficients of-0.117%℃-（-1）（α） and-0.74%℃-（-1）（β） in the regular magnets without Dy（80）Ga（20） powder.The irreversible loss of magnetic flux（Hirr） was investigated at different temperatures.After being exposed to 150 ℃ for 2 h,the Hirr of magnets with 4 wt.%Dy（80）Ga（20） decreased by -95%compared to that of the undoped magnets.The enhanced temperature coefficients and Hirr indicate improved thermal stability in the doped Nd-Fe-B magnets.The intergranular addition of Dy（80）Ga（20） also improved the corrosion resistance of the magnets because of the enhanced intergranular phase.In a corrosive atmosphere for 96 h,the mass loss of the sintered magnets with 4 wt.%Dy（80）Ga（20） was 2.68 mg/cm-2,less than 10%of that suffered by the undoped magnets（28.1 mg/cm-2）.
To investigate the coercivity,corrosion resistance,and thermal stability of Nd-Fe-B magnets,their properties were investigated at room and high temperature before and after doping with Dy（80）Ga（20）（at.%） powder.The coercivity of the magnets increased from the undoped value of 12.72 kOe to a doped value of 21.44 kOe.A micro-structural analysis indicates that a well-developed core-shell structure forms in the magnets doped with Dy（80）Ga（20） powder.The improvement in magnetic properties is believed to be related to the refined and uniform matrix grains,continuous grain boundaries,and a hardened（Nd,Dy）2Fe（14）B shell surrounding the matrix grains.Additionally,the doped magnets exhibit an obvious improvement in thermal stability.For the magnets with added Dy（80）Ga（20） powder,the temperature coefficients of remanence（α） and coercivity（β） increased to-0.106%℃-（-1） and-0.60%℃-（-1） over the range 20-100 ℃,compared to temperature coefficients of-0.117%℃-（-1）（α） and-0.74%℃-（-1）（β） in the regular magnets without Dy（80）Ga（20） powder.The irreversible loss of magnetic flux（Hirr） was investigated at different temperatures.After being exposed to 150 ℃ for 2 h,the Hirr of magnets with 4 wt.%Dy（80）Ga（20） decreased by -95%compared to that of the undoped magnets.The enhanced temperature coefficients and Hirr indicate improved thermal stability in the doped Nd-Fe-B magnets.The intergranular addition of Dy（80）Ga（20） also improved the corrosion resistance of the magnets because of the enhanced intergranular phase.In a corrosive atmosphere for 96 h,the mass loss of the sintered magnets with 4 wt.%Dy（80）Ga（20） was 2.68 mg/cm-2,less than 10%of that suffered by the undoped magnets（28.1 mg/cm-2）.
基金
Project supported by the Ministry of Science and Technology of China(Grant Nos.2014DFB50130 and 2011CB612304)
the National Natural Science Foundation of China(Grant Nos.51172168 and 51072139)
