The corrosion-resistant coating formed on the surface of sintered Nd-Fe-B magnet by a phosphate chemical conversion(PCC)treatment was studied.The morphology,phase composition and thickness of the coating were investig...The corrosion-resistant coating formed on the surface of sintered Nd-Fe-B magnet by a phosphate chemical conversion(PCC)treatment was studied.The morphology,phase composition and thickness of the coating were investigated by field emission scanning electron microscopy(FE-SEM),energy-dispersive spectrometer(EDS),Fourier transform infrared(FTIR)spectrometer and coating thickness gauge.The corrosion behaviour of the phosphated magnet was evaluated by copper sulphate spot test,neutral salt spray test and electrochemical potentiodynamic polarization experiment.The magnetic properties of the phosphated magnet were also tested.The experimental results show that the phosphate coating has such characteristics as dense granular growth,uniform distribution and thickness range of 10-18μm.The corrosion resistance of the magnet is significantly improved by phosphate coating without losing magnetic properties.Therefore,this highly efficient PCC was a good way for increasing the corrosion resistance of the sintered Nd-Fe-B magnets.展开更多
The brittleness and fracture behaviors of the sintered and the two-stage aged Dy-doped NdFeB magnets were studied by a unique method of acoustic emission testing and Vickers hardness indentation method in this paper.A...The brittleness and fracture behaviors of the sintered and the two-stage aged Dy-doped NdFeB magnets were studied by a unique method of acoustic emission testing and Vickers hardness indentation method in this paper.A detailed analysis on the crack propagation mechanism along the grain boundary of the main grain phase(Nd,Dy)_(2)Fe_(14)B was done.By comparing the acoustic emission energy count value(E_(n))with the Vickers hardness indentation load(P),it is shown that there is a linear relationship between En and P for both the sintered and the two-stage aged Dy-doped NdFeB magnets.According to the slope of En versus P linear lines,it can be found that the two-stage aged Dy-doped NdFeB magnet is more brittle than the sintered one.It is due to that the Ndrich grain boundary phase of the two-stage aged Dy-doped NdFeB magnet is formed as thin film and uniformly distributes around the main grain phase,which plays a significant role in increasing the intrinsic coercive force of the magnet,but decreasing its interface binding strength.Therefore,the resistance of crack propagation along the grain boundary decreases and the brittleness increases.展开更多
基金financially supported by the China National Major Special Project for the Rare Earth and Rare Metallic Materials(No.(2012)1743)。
文摘The corrosion-resistant coating formed on the surface of sintered Nd-Fe-B magnet by a phosphate chemical conversion(PCC)treatment was studied.The morphology,phase composition and thickness of the coating were investigated by field emission scanning electron microscopy(FE-SEM),energy-dispersive spectrometer(EDS),Fourier transform infrared(FTIR)spectrometer and coating thickness gauge.The corrosion behaviour of the phosphated magnet was evaluated by copper sulphate spot test,neutral salt spray test and electrochemical potentiodynamic polarization experiment.The magnetic properties of the phosphated magnet were also tested.The experimental results show that the phosphate coating has such characteristics as dense granular growth,uniform distribution and thickness range of 10-18μm.The corrosion resistance of the magnet is significantly improved by phosphate coating without losing magnetic properties.Therefore,this highly efficient PCC was a good way for increasing the corrosion resistance of the sintered Nd-Fe-B magnets.
基金financially supported by the China National Major Special Project for the Rare Earth and Rare Metallic Materials ((2012) 1743)
文摘The brittleness and fracture behaviors of the sintered and the two-stage aged Dy-doped NdFeB magnets were studied by a unique method of acoustic emission testing and Vickers hardness indentation method in this paper.A detailed analysis on the crack propagation mechanism along the grain boundary of the main grain phase(Nd,Dy)_(2)Fe_(14)B was done.By comparing the acoustic emission energy count value(E_(n))with the Vickers hardness indentation load(P),it is shown that there is a linear relationship between En and P for both the sintered and the two-stage aged Dy-doped NdFeB magnets.According to the slope of En versus P linear lines,it can be found that the two-stage aged Dy-doped NdFeB magnet is more brittle than the sintered one.It is due to that the Ndrich grain boundary phase of the two-stage aged Dy-doped NdFeB magnet is formed as thin film and uniformly distributes around the main grain phase,which plays a significant role in increasing the intrinsic coercive force of the magnet,but decreasing its interface binding strength.Therefore,the resistance of crack propagation along the grain boundary decreases and the brittleness increases.
