The corrosion resistance and magnetostriction of(Tb0.3Dy0.7)Fe2 alloy were investigated for different nitrogen doses of 5×1015, 5×1016, 5×1017, 1×1018 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% NaCl 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 5×1017 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 nitrogen ion implantation on the magnetostrictive properties turned out to be small. Finally, a model was applied to interpret the influence of nitrogen implantation on the magnetostriction in the light of the information provided by the experimental results in this study.
The LaFe11.9–x Cox Si1.1B0.25with x=0.9 and x=0.82 compounds were synthesized from commercial purity raw materials.The magnetic property of LaFe11.9–x Cox Si1.1B0.25and Gd particles were tested on the reciprocating refrigerator at the same condition in order to compare the cooling capacity of the two materials.The results showed that the cooling velocity of Gd was obviously higher than that of LaFe11.9–x Cox Si1.1B0.25.The maximum temperature span was 12.7 oC for LaFe11.0Co0.9Si1.1B0.25,14.9 oC for Gd metal whose mass is the same as that of LaFe11.0Co0.9Si1.1B0.25,8.1 oC for Gd metal whose volume is the same as that of LaFe11.0Co0.9Si1.1B0.25.Series connection of LaFe11.0Co0.9Si1.1B0.25and LaFe11.08Co0.82Si1.1B0.25had the maximum cooling temperature span of 15.3 oC.
Microstructure dependent on silicon and formation of 1:13 phase in LaFe13-ySiyC0.2 compounds was investigated. C and Si ele-ments played different roles in assisting the formation of 1:13 phase. Si could inhibit the growth of α-Fe. The volume fraction of La-rich phase increased with the increase of Si content in the LaFe13-ySiyC0.2 ingots. When Si content was lower in LaFe13-ySiyC0.2 (y≤1.0), α-Fe was excess and grew very large in the initial annealing process. As a result, a large amount of α-Fe remained even after a long time annealing process. Carbon doping could accelerate the formation of 1:13 phase in the LaFe13-ySiyC0.2 compounds. The amount of the 1:13 phase reached ~90 vol.% in LaFe13-ySiyC0.2 (y≥1.2) after annealing at 1353 K for only 3 d. After optimized annealing, large magnetic entropy changes were ob-tained in LaFe13-ySiyC0.2 compounds (18.6 and 15 J/(kg·K) in 0-2 T field change for y=1.2, 1.4, respectively).
Effect of impurity phase(α-Fe phase and La-rich phase) on corrosion resistance and magnetic entropy change of LaFe_(11.3)Co_(0.4)Si_(1.3)C_(0.15) compound was studied using scanning electron microscopy, potentiodynamic polarization, electrochemical impedance spectroscopy techniques and magnetism testing. With the decrease of impurity phase, the corrosion resistance of LaFe_(11.3)Co_(0.4)Si_(1.3)C_(0.15) compound was first enhanced and then slightly impaired. Corrosion resistance could be significantly improved by the decrease of α-Fe phase. However, the matrix phase was corroded if the La-rich phase as anode was too few. This caused the corrosion resistance to decrease slightly. After immersing the sample in distilled water for 15 d, –?S_(max) of the samples annealed for 3, 12 h, 3 and 7 d decreased about 50%, 41%, 16% and 17%, respectively.
