The corrosion resistance and magnetostriction of （Tb0.3Dy0.7）Fe2 alloy were investigated for different nitrogen doses of 5Х 1015, 5Х 1016, 5Х 1017, 1 Х 1018 ions/cm2 and average ion energy of 140 kV. The phase and elements concentration in the implanted layer were examined by X-ray diffraction and auger electron spectroscopy, respectively. The aqueous corrosion studies were carried out in 3.5% NaC1 solutions. It was found that corrosion resistance had improved substantially with respect to the untreated substrates. The corrosion resistance was maximum at a dose of 5x1017 ions/cm2, and saturation in corrosion improvement was noticed at a higher dose, 10~ 1017 ions/cm2. In contrast, the results of magnetostriction tests before and after ion implantation showed that the influence of ni- trogen ion implantation on the magnetostrictive properties turned out to be small. Finally, a model was applied to interpret the influ- ence of nitrogen implantation on the magnetostriction in the light of the information provided by the experimental results in this study.
Effect of ion nitriding modification on surface hardness, corrosion resistance and magnetostriction of （Tb0.3Dy0.7）Fe1.95 alloy was investigated. Results demonstrated that a 100-200 nm thick nitrided layer was formed on the sample surface by ion nitriding treatment, which improved obviously surface hardness, wear, and corrosion resistance properties of （Tb0.3Dy0.7）Fe1.95 alloys. The surface hardness was increased from HV587 to HV622 after ion nitriding at 650 K for 6 h. Furthermore, ion nitriding treatment had almost no influence on mag- netostrictive performance as the nitrided layer was quite thin and the treatment temperature was not too high. The results might provide us a new approach for surface modification of （Tb0.3Dy0.7）Fe1.95 alloy.
Effects of nitriding modification on surface phase structure, morphology, corrosion resistance and magnetostriction of （Tb,Dy）Fe2 alloy were investigated by nitrogen ion implantation. Results showed that the surface REFe2 phase gradually decomposed and transformed into REN, α-Fe and Fe8N phases with the increase of nitrogen ion implantation dose. The surface morphology of the alloy had an obvious change after nitrogen ion implantation. The corrosion resistance properties of the alloy in acidic, alkaline and chloridion environment were also greatly improved. In addition, the magnetostriction performance of the alloy was almost not affected by ion implantation as the nitrided layer was quite thin and the operating temperature was very low. The results proved that nitrogen ion implantation was an effective method for surface modification of （Tb,Dy）Fe2 alloy.
The surface of Tb_(0.3)Dy_(0.7)Fe_(2) alloys was modified by microwave electron-cyclotron-resonance chemical vapor deposition(MW-ECR-CVD)and ion implantation technology,respectively.The microstructure and corrosion resistance of nitrided layers were investigated by means of optical microscope(OM),X-ray diffractomer(XRD),auger electron spectroscopy(AES),and electrochemical workstation.After modified by MW-ECR-CVD,the nitrogen concentration of the nitrided layers decreases gradually with the depth increasing,while the nitrogen concentration modified by ion implantation process exhibits Gaussian distribution.The self-corrosion electric potential of the sample modified by ion implantation is higher than that modified by MW-ECR-CVD,which reveals that the samples modified by ion implantation process have a better resistance to corrosion.The magnetostrictions are assessed for the samples placed in the air for one year,which further confirms that the ion implantation process is more helpful to maintain the magnetostrictions.
Hong-Chuan YangShi-Rong ZhangDun-Bo YuKuo-She LiYuan-Fei YangQuan-Xia HuYang LuoHong-Wei Li
