• Transactions of Materials Processing
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• v.7 no.4
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• pp.333-339
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• 1998

Hot torsion tests were conducted to investigate the high temperature deformation behavior of $Al_{85}Ni_{10}Y_5$ alloy extrudates fabricated with amorphous ribbons. The powder metallurgy routes, hot pressing and hot extrusion were used to fabricate the extrudates. Thermal properties of amorphous ribbons with different thickness as a function of aging temperature were studied by thin film x-ray dif-fraction (XRD) and differential scanning calorimetry(DSC). The Al phase crystallite firstly formed in the amorphous ribbons and its crystallization temperature($T_x$)Was ~210${\circ}C$ During the processings of consolidation and extrusion, nano-grained structure(~100 nm) was formed in the Al85Ni10Y5 alloy extrudates. The as-extrudated Al85Ni10Y5 alloy and the $Al_{85}Ni_{10}Y_5$ alloy annealed at 250${\circ}C$ for 1 hour showed a flow curve of DRV(dynamic recovery) during hot deformation at 400-550${\circ}C$. On the other hand, the $Al_{85}Ni_{10}Y_5$ alloy annealed at 400${\circ}C$ for 1 hour showed a flow curve of DRX(dynamic recrys-tallization) during hot deformation at 450-500${\circ}C$. Also the flow stress and flow strain of the $Al_{85}Ni_{10}Y_5$ alloy extrudate annealed at 400${\circ}C$ were higher than those at 250${\circ}C$.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.341-345
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• 1998

Magnetic shielding effect of cylinderical ahields made of commericial amorphous ribbons has been studied. The shell-arrangement-order of double shell shield has been found to show a striking differencein shielding factor. In low applied field region, a 2605CO-2705M-shield (outer shell: 2605CO, inner shell: 2705M) yields two times higher shielding factor than a 2705M-2605CO-shield (outer shell: 2705M, inner shell: 2605CO). The reasons are as follows: In case of 2605CO-2705M-shield, the outer shell is not easily saturated and effectively shields the applied field. In addition, the inner shell shows high shielding factor in the field shielded by the outer shell. In case of 2705M-2605CO-shield, the outer shell is saturated at very low-field as well as the inner shell shows low shielding factor in the field shielded by the outer shell.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.3
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• pp.236-243
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• 1995

Since amorphous alloys have been known to have better mechanical and chemical properties than crystalline alloys of the same composition, a great number of studies on the formation of Al-based amorphous alloys have been carried out actively. However, little has been obtained about the effect of Rare-Earth metal and Transition metal addition on amorphous phase formed by melt spinning method. This study included fabrication of amorphous alloy $Al_{85}Ce_5Ni_{10}$ by melt spinning methods and DTA, XRD, TEM analysis to determine crystalization behavoir. Annealing treatments were carried out in Ar atmosphere under isothermal and nonisothermal conditions. The diffraction pattern of non-heated ribbons showed broad form characteristic of glass metallic alloy. The crystallization of amorphous $Al_{85}Ce_5Ni_{10}$ takes place eutedtoidly by homogeneous formation of Al and MS-1, followed by precipitation of the $Al_{11}Ce_3$ and later $MS-1{\rightarrow}Al_3Ni$ transformation.

• Journal of Korea Foundry Society
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• v.28 no.1
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• pp.31-36
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• 2008

Ti-Ni-Cu alloys are very attractive shape memory alloys for applications as actuators because of a large transformation elongation and a small transformation hysteresis. Rapidly solidified Ti-Ni alloy ribbons have been known to have the shape memory effect and superelasticity superior to the alloy ingots fabricated by conventional casting. In this study, solidification structures and shape memory characteristics of $Ti-Ni_{30}-Cu_{20}$ alloy ribbons prepared by melt spinning were investigated by means of DSC and XRD. Operating parameters to fabricate the amorphous ribbons were the wheel velocity of 55 m/s and the melt spinning temperature of $1500^{\circ}C$. The crystallization temperature was measured to be $440^{\circ}C$. The crystallized ribbons exhibited very fine microstructure after annealing at $440^{\circ}C$ for 10 minutes and $460^{\circ}C$ for 5 minutes and was deformed up to about 6.8% and 6.23% in ductile manner, respectively. Stress-strain curve of the ribbon exhibited a flat stress-plateau at 64 MPa and this is associated with the stress-induced a B2-B19 martensitic transformation. During cycle deformation with the applied stress of 220 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be $4.3^{\circ}C$ and 3.6%.

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.191-197
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• 2005

In the fabrication process of Fe-based amorphous alloy powder cores by pulverization of the melt-spun ribbons and cold compaction, the effects of powder preparation method on the magnetic & electric properties, powder shapes and microstructure of cores have been investigated. The powder cores made by using rotor mill showed low effective permeability as compared to the cores prepared by ball milling. However the frequency dependence and quality factor properties were superior in the case of rotor-milling. Further the powders prepared by rotor mill had homogeneous and round shapes through strong shearing in the sieve ring, while the ball milled powders were inhomogeneous and relatively small. The lower permeability of the powder cores fabricated with rotor mill was considered to be due to the high internal stress occurred by very intensive shearing. Moreover the powder cores produced by rotor-milling showed lower core loss and good frequency dependence of effective permeability possibly due to the higher electrical insulation between magnetic particles. The dc bias property of the powder cores made by rotor-milling was better than the one by ball-milling.

• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.67-73
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• 2015

This is a basic research for improving soft magnetic property of Fe based nano crystalline alloy powder core. The main study is done around characteristics of permeability, core loss, and DC bias depending on amount of insulation coating agent and particle size. First, $Fe_{73.5}Si_{13.5}B_9Nb_3Cu_1$ amorphous alloy ribbon was fabricated by using the planar flow casting (PFC) device. Then, heat treatment and ball milling were done to obtain alloy powder. The amount of polyether imide (PEI) added to it was varied by 0.5, 1.0, 2.0, 2.5 wt% to have compression molding into $16ton/cm^2$. After going through crystalline heat treatment, the made toroidal nano crystalline powder core ($OD12.7mm^*ID7.62mm^*H4.75mm$) had smaller permeability as amount of insulation coating agent decreases. However, it was found out that core loss and DC bias characteristics have been improved. The reason for this results were expected to be because green density of power core decreases as amorphous alloy powder particles become smaller as amount of alloy powder insulation coating agent increases, it was determined that 1 wt% of insulation coating agent is appropriate. Also, for powder core made based on alloy powder size with amount of insulation coating agent fixed at 1 wt%, effective permeability and core loss were outstanding as particle size became bigger. However, characteristics of DC bias became worse as applied DC field increases. This is expected to be due to insulation effect, residual pores, or molding density of powder core resulting from thickness of coating on surface of alloy powder.

• Journal of the Korean Magnetics Society
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• v.11 no.3
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• pp.85-96
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• 2001

Experimental magnetization-temperature curves for melt-spun ribbons of amorphous alloys (Dy$\_$0.33/Fe$\_$0.67/)$\_$1-x/B$\_$x/(x=0 ,0.05, 0.1, and 0.15) and (Sm$\_$0.33/Fe$\_$0.67/)$\_$1-x/B$\_$x/(x=0, 0.01, 0.02, and 0.03) (in atomic fraction) are fitted with theoretical equations based on the mean field theory in order to calculate exchange couplings between constituent elements as a function of the B content. In the case of the DyFe$_2$-B system, the sign of the exchange coupling between Dy and Fe is negative, indicating that the magnetization direction of Dy is antiparallel to that of Fe. The sign of the other two couplings are positive indicating a parallel alignment. The exchange coupling between Fe ions are greatest, while that between Dy ions is negligible. In the case of the SmFe$_2$B alloys, the sign of all the couplings are positive, indicating ferromagnetic coupling between the spins. The exchange couplings between Fe ions, and Fe and Sm are comparable to each other, but they are much greater than that between Sm ions. The high exchange coupling between Fe and Sm, which is considered to occur indirectly, is rather unexpected, but it is considered to be unique characteristics of amorphous Sm-Fe alloys. In both alloy systems, the exchange coupling between Fe ions increases with increasing B content. and this may be explained by the increase of the Fe-Fe separation with increasing B content. The exchange coupling between Fe and RE also increases with increasing B content. As the B content increases, the magnetization decreases over the whole temperature range, and the Curie temperature also decreases.

• Journal of the Korean Magnetics Society
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• v.17 no.5
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• pp.198-204
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• 2007

The effects of annealing temperature on electromagnetic wave absorption characteristics in $Fe_{73.5}Cu_1Nb_3Si_{15.5}B_7$ (at%) alloy flakes/polymer composite sheets available for quasi-microwave band have been investigated. The composite sheet including the magnetic flakes annealed at $425{\sim}475^{\circ}C$ for 1 h exhibited highest power loss in the GHz frequency range as compared with the sheets composed of the alloy flakes annealed at higher temperature than $475^{\circ}C$ or in as-milled state. Moreover the imaginary part of complex permeability had largest value in the GHz frequency range for the sheets including the flakes annealed at $425{\sim}475^{\circ}C$. The large value of power loss of the sheets including the magnetic flakes annealed at $425{\sim}475^{\circ}C$ was attributed to the high imaginary part of the complex permeability. However, because of its large transmission parameter $S_{21}$, the composite sheet having the magnetic flakes annealed at $525^{\circ}C$ showed low power loss.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1063-1069
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• 1997

For me1t-spun Fe-Nd-C alloys, variation of phase development and magnetic properties with the variety of alloy compositions and production conditions were investigated. To find out whether hard magnetic $Fe_{14}Nd_2C$ is crystallized direct1y from the melt by rapid quenching, the phase development of the as-spun ribbons spun at various speed was a1so studied. For the ribbons spun at 10m/s, ${\alpha}-Fe$ was the primary crystallization phase followed by the secondary $Fe_{17}Nd_2C$. At 20m/s ${\alpha}-Fe$ was suppressed so that the primary $Fe_{17}Nd_2C$ coexisted with the secondary ${\alpha}-Fe$ and the amorphous phase. Above 30m/s the ribbons were a1most amorphous, and the amorphization was complete at 40m/s. $Fe_{14}Nd_2C$ therefore was not found in as-spun state but obtained after heat treating the ribbons. The effective temperature range ($700{\sim}900^{\circ}C$) in which $Fe_{14}Nd_2C$ can be obtained was wider than that of a cast alloy. An alloy made with the wheel speed of 20 or 30m/s yielded higher coercivities after heat treatment. In iron-rich Fe-Nd-C, the composition range in which a high coercivity (more than 10kOe) is expected is narrow, i.e., 77~78 Fe and 7~8 C(at.%).

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.864-873
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• 1995

Amorphous $Fe_{73.5}Cu_{1}Nb_{3}Si_{16.5}B_{6}$ ribbons were annealed for different time at $500^{\circ}C$ and $552^{\circ}C$, just before and after the exothermic reaction in DSC curve. The development of nanocrystalline phase was investigated by means of $M\"{o}ssbsuer$ spectroscopy. The crystalline phase consists mainly of $DO_{3}Fe-Si$. Though slight in amount (5%), another ferromagnetic phase which could be presumed $t-Fe_{3}B$ was detected Si content of $DO_{3}Fe-Si$, Si/(Fe+Si), was 0.218 under the heat treatment at $500^{\circ}C$ for 60 min and 0.222 at $552^{\circ}C$ for 10 min. Since then both of those values decreased with time until 120 min and finally these two values remained constant at 0.210. The variation in Si content with annealing time results in the variation in the hyperfine field and the isomer shift. The increase in the mean hyperfine fields and the decrease in the mean isomer shifts of Fe-Si are caused by the increase in Si content. The volume fractions of residual amorphous phase rapidly decrease during the early stage of annealing and come nearer to saturation after 120 min both at $500^{\circ}C$ and $552^{\circ}C$. The decrease in the mean hyperfine field of residual amorphous. in spite of slight changes in the volume fractions of Fe-Si and of residual amorphous after 120 min. is caused by the increase in the content of Nb and B in residual amorphous phase. The saturated volume fraction of the crystalline phase was 81% for $500^{\circ}C$ (180 min) and 77% for $552^{\circ}C$ (960 min), different from expectation.