Papers by Keyword: Melt-Spun

Abstract: In this work, the effects of substitution of Nd by Gd on the magnetic properties of Nd-Fe-B magnets were investigated. The results demonstrate that the size of grain decreases with the addition of Gd element. The Curie temperatures (Tc) are found to improve with the increase in Gd content, which means that the thermal stability of the magnets is enhanced. The coercivity and saturation magnetization decrease with the increase in Gd content due to the low magnetocrystalline anisotropy and saturation magnetization of Gd₂Fe₁₄B.

Abstract: The magnetic phase transition and magnetic entropy change of melt-spun LaFe_11.6Si_1.4B_x (x=0.0, 0.3, 0.5, 0.7) ribbons were investigated by measuring the magnetization as the function of temperature. Comparing with LaFe_11.6Si_1.4, the NaZn₁₃-type structure of LaFe_11.6Si_1.4B_x did not change after introducing B atoms, while the amount of α-Fe phase in the ribbons significantly decreased. The Curie temperature slightly changes after the addition of B. The LaFe_11.6Si_1.4B_x (x=0.3, 0.5) exhibits first-order magnetic transition and large magnetic entropy change as observed in LaFe_11.6Si_1.4 compound.

Abstract: Influence of nanoflakes and melt-spun ribbons on the nitrogenation temperature f Sm₂Fe₁₇ was investigated. The microstructure, phase structure, properties of the specimens before and after nitrogenation have been discussed. It is interesting found that hard magnetic Sm₂Fe₁₇N₃ flakes have been synthesized by surfactant-assisted high energy ball milling and nitriding Sm2Fe17 in 3 psi of N2 gas at lower temperature 300 °C and 350 °C for 3 h. The synthesized Sm₂Fe₁₇N₃ flakes still retained nanostructure and obtained a coercivity of 3.56 kOe. For the melt-spun ribbons, it needs a higher nitrogenation temperature and longer time to obtain the same coercivity values as the nanoflakes.

Abstract: At room temperature, Fe-15Mn-5Si-9Cr-5Ni alloys are usually austenitic and the application of a stress induces a reversible martensitic transformation leading to a shape memory effect (SME). However, when a ribbon of this material is obtained by melt-spinning, the rapid solidification stabilizes a high-temperature ferritic phase. The goals of this work were to find the appropriate heat treatment in order to recover the equilibrium austenitic phase, characterize the ribbon form of this material and evaluate its shape memory behaviour. We found that annealing at 1050°C for 60 min, under a protective argon atmosphere, followed by a water quenching stabilizes the austenite to room temperature. The yield stress, measured by tensile tests, is 250 MPa. Shape-memory tests show that a strain recovery of 55% can be obtained, which is enough for certain applications.

Abstract: The microstructure and magnetic properties of melt-spun nanocomposite (Nd, Dy, Pr)-(Fe,Nb,Zr)-B /α-Fe ribbons have been investigated by XRD, SPM and VSM. The ribbons were prepared at a wheel speed range of 10-30 m/s. The multigrain domain or interaction domain was observed in the samples prepared at 20 m/s wheel speed. The easy magnetized direction c-axis parallel to the ribbon plane for the sample prepared at the wheel speed of 20m/s. The average gain size in this sample is about 18nm and the sample consists of hard magnetic phase (Nd, Dy, Pr) ₂(Fe,Nb,Zr)14B and sofe magnetic phase α-Fe, there is strong exchange-coupling interaction between them. The magnetic properties obtained are B_r=1.28T，H_ci= 504.2kA•m^-1，(BH)_max= 157.8 kJ•m^-3，M_r/M_s =0.76.

Abstract: A series of Al-Cu-Si alloys were melted and spun into ribbons of about 100m thickness. The alloy compositions were selected to be suitable for brazing below 580C as filler metals. In the as-quenched state the foils were relatively brittle due to the occurrence of metal metastable phases. After appropriate annealing treatments between 400~450C the metastable phases were transformed into fine (Cu2Al) particles within the -Al matrix, and the mechanical properties of the Al-Cu-Si alloy ribbons were considerably improved.

Abstract: The effect of the quenched speed on the microstructure and electromagnetic properties of melt spun Nd3Fe₆₈Co₁₈B₁₁ nanocomposites was investigated. XRD spectra showed that only α-Fe phase can be obtained for both quenched samples. The complex permeability () and permittivity () within 2-18GHz were measured by vector network analysis. By virtue of quenched speed increased, the flake-like Nd₃Fe₆₈Co₁₈B₁₁ decreased the value of permittivity while that of permeability slightly changed. According to transmission line theory, the reflection loss was calculated. With thin matching thickness of 1.5mm, The Nd₃Fe₆₈Co₁₈B₁₁ composites realized the optimum reflection loss RL=-5.3dB at 3.6GHz and RL=-3.5dB at 3.9GHz for quenched speed 30m/s and 20m/s, respectively. It showed that it is possible to obtain good microwave absorbing properties with appreciated quenched speed for as spun Nd-Fe-B nanocomposites.

Abstract: Nanocompositesα-Fe/Fe₃B/Y₂O₃ and ε-Fe₃N/Y₂O₃ were prepared by a melt-spun technique, and the subsequent hydrogenation, oxidation and nitrogenation treatments, respectively. The effective electromagnetic wave absorption (RL<-20 dB) was obtained in a frequency range of 2.7-6.5 GHz on resin composites of 80 wt% α-Fe/Fe₃B/Y₂O₃ powders, with thickness of 6-3 mm; the ε-Fe₃N/Y₂O₃ resin composites exhibited good microwave absorption properties in the 0.6-4.4 GHz range.