Infiltration is a popular technique used to produce valve seat rings and guides to create dense parts. In order to develop valve seat material with a good thermal conductivity and thermal expansion coefficient, Cu-infiltrated properties of sintered Fe-Co-M(M=Mo,Cr) alloy systems are studied. It is shown that the copper network that forms inside the steel alloy skeleton during infiltration enhances the thermal conductivity and thermal expansion coefficient of the steel alloy composite. The hard phase of the CoMoCr and the network precipitated FeCrC phase are distributed homogeneously as the infiltrated Cu phase increases. The increase in hardness of the alloy composite due to the increase of the Co, Ni, Cr, and Cu contents in Fe matrix by the infiltrated Cu amount increases. Using infiltration, the thermal conductivity and thermal expansion coefficient were increased to 29.5 W/mK and 15.9 um/moC, respectively, for tempered alloy composite.

In this paper, a new Co10Fe10Mn35Ni35Zn10 high entropy alloy (HEA) is identified as a strong candidate for the single face-centered cubic (FCC) structure screened using the upgraded TCFE2000 thermodynamic CALPHAD database. The Co10Fe10Mn35Ni35Zn10 HEA is fabricated using the mechanical (MA) procedure and pressure-less sintering method. The Co10Fe10Mn35Ni35Zn10 HEA, which consists of elements with a large difference in melting point and atomic size, is successfully fabricated using powder metallurgy techniques. The MA behavior, microstructure, and mechanical properties of the Co10Fe10Mn35Ni35Zn10 HEA are systematically studied to understand the MA behavior and develop advanced techniques for fabricating HEA products. After MA, a single FCC phase is found. After sintering at 900℃, the microstructure has an FCC single phase with an average grain size of 18 μm. Finally, the Co10Fe10Mn35Ni35Zn10 HEA has a compressive yield strength of 302 MPa.

This study was carried out to investigate the effect of grain size on the damping capacity of the Fe-26Mn-4Co-2Al damping alloy. α’ and ε-martensite were formed by cold working, and these martensites were formed with a specific direction and surface relief. With an increase in grain size, the volume fraction of α’ and ε-martensite increased by decrement the austenite phase stability. This volume fraction more rapidly increased in cold-rolled specimen than in the specimen that was not cold-rolled. The damping capacity also increased more with the augmentation an increased grain size and more rapidly increased in cold-rolled specimen than in the specimen that was not cold rolled. The effect of grain size on the damping capacity was larger in the cold-rolled specimen than the specimen that was not cold-rolled. Damping capacity linearly increased with an increase in volume fraction of ε-martensite. Thus, the damping capacity was affected by the ε-martensite.

This study was carried out to investigate the effect of deformation induced martensite on the damping capacity of Fe-26Mn-4Co-2Al damping alloy. α‘ and ε-martensite were formed by cold working, and; deformation induced martensite was formed with according to the specific direction and the surface relief. With an increasing degree of cold rolling, the volume fraction of α‘-martensite increased rapidly, while the volume fraction of ε-martensite decreased after rising to a maximum value at a specific level of cold rolling. Damping capacity was increased, and then decreased with an increasing of the degree of cold rolling. Damping capacity was influenced greatly by the volume fraction of ε-martensite formed by cold working, but the effect of the volume fraction of α‘-martensite have a actually on effect on the damping capacity.

The effect of alpha phase on the fatigue properties of Fe-29%Ni-17%Co low thermal expansion alloy was investigated. Two kinds of alloys (Base alloy and Alpha alloy) were prepared by controlling the minimal alloy composition. Microstructure observation, tensile, high-cycle fatigue, and low-cycle fatigue results were measured in this study. The Base alloy microstructure showed typical austenite γ phase. Alpha alloy represented the dispersed phase in the austenite γ matrix. As a result of tensile testing, Alpha alloy was found to have higher strengths (Y.S. & T.S.) and lower elongation compared to those of the Base alloy. High cycle fatigue results showed that Alpha alloy had a higher fatigue limit (360MPa) than that (330MPa) of the Base alloy. The Alpha alloy exhibited the superior high cycle fatigue property in all of the fatigue stress conditions. SEM fractography results showed that the alpha phase could act to effectively retard both fatigue crack initiation and crack propagation. In the case of low-cycle fatigue, the Base alloy had longer fatigue life in the high plastic strain amplitude region and the Alpha alloy showed better fatigue property only in the low plastic strain amplitude region. The fatigue deformation behavior of the Fe-29%Ni-17%Co alloy was also discussed as related with its microstructure.

Magnetic properties of nanostructured materials are affected in complicated manner by their microstructure such as pain size (or particle size), internal strain and crystal structure. Thus, studies on the synthesis of nanostructured materials with controlled microstructure are necessary fur a significant improvement in magnetic properties. In the present work, nanostructured Fe-Co alloy powders with a grain size of 50 nm were successfully fabricated from the powder mixtures of (99.9% purity) and by chemical solution mixing and hydrogen reduction.

Magnetic properties of nanostructured materials are affected by the microstructures such as grain size (or particle size), internal strain and crystal structure. Thus, it is necessary to study the synthesis of nanostructured materials to make significant improvements in their magnetic properties. In this study, nanostructured Fe-20at.%Co and Fe-50at.%Co alloy powders were prepared by hydrogen reduction from the two oxide powder mixtures, and . Furthermore, the effect of microstructure on the magnetic properties of hydrogen reduced Fe-Co alloy powders was examined using XRD, SEM, TEM, and VSM.

In this study, chemical solution mixing and hydrogen reduction method was used to fabricate nanostructured alloy powders. Fe-Co chloride mixture, FeCl and COCI with 99.9％ purity, were reduced in hydrogen atmosphere. Nanostructured Fe-Co alloy powders with a grain size of 50 nm were successfully fabricated. Magnetic properties of fabricated (x=0, 10, 30, 50, 70, 100) alloy powders with the same grain size were measured because size factor can affect magnetic properties. Coercivity of Fe-Co alloy powders were increased with increasing Co contents. Maximum value of coercivity in various Co contented Fe-Co alloy powders with similar grain size was 125 Oe at Fe. Saturation magnetization value at FeCo composition showed maximum value of 219 emu/g and saturation magnetization value decreased with increasing Co contents and minimum value of 155 emu/g was observed at Co.

The purpose of this study is the fabrication of nano-sized Fe-Co alloy powders with soft magnetic properties by the slurry mixing and hydrogen reduction (SMHR) process. 0 and powders with 99.9% purities were used for synthesizing nanostructured Fe-Co alloy powder. Nano-sized Fe-Co alloy powders were successfully fabricated using SMHR, which was performed at 50 for 1 h in H atmosphere. The fabricated Fe-Co alloy powders showed ' phase (ordered body centered cubic) with the average particle size of 45 nm. The SMHR powder exhibited low coercivity force of 32.5 Oe and saturation magnetization of 214 emu/g.

Conventional Fe-Co alloys are important soft magnetic materials that have been widely used in industry. Compared to its polycrystalline counterpart, the nanostructured materials have showed superior magnetic properties, such as higher permeability and lower coercivity due to the single domain configuration. However, magnetic properties of nanostructured materials are affected in complicated manner by their microstructure such as grain size, internal strain and crystal structure. Thus, studies on synthesis of nanostructured materials with controlled microstructure are necessary for a significant improvement in magnetic properties. In the present work, starting with two powder mixtures of Fe and Co produced by mechanical alloying (MA) and hydrogen reduction process (HRP), differences in the preparation process and in the resulting microstructural characteristics will be described for the nano-sized Fe-Co alloy particles. Moreover, we discuss the effect of the microstructure such as crystal structure and grain size of Fe-Co alloys on the magnetic properties.

본 연구에서는 기계적 합금화 공정을 통하여 평균 10nm의 크기를 가지는 결정립으로 이루어지는 나노구조 Fe-Co 합금분말을 제조하였으며 제조된 합금분말을 PECS 공정으로 소결하여 벌크의 나노구조 Fe-Co 연자성 합금을 제조하고자 하였다. PECS 공정은 소결온도를 700, 800, 900과 1000˚C로 변화시키고 유지시간을 0에서 16분가지 변화시켜주며 수행하였다. PECS 공정의 나노구조 소결체 제조에 관한 효율성을 평가하였으며 소결온도와 유지시간의 변화에 따른 소결밀도와 미세구조의 변화를 관찰하여 최적의 소결조건을 찾고자하였다. 또한 각 소결조건에서 제조된 소결체들의 보자력과 포화자화값을 측정하여 자성특성을 평가하였다.

증착법을 이용하여 Sm(Co1-xFex) 및 Sm2(Co1-xFex)17(X=0, 0.3,0.5,0.7)박막을 제작하여 조성변화 및 열처리 온도 변화에 따른 자기적 성질의 변화에 대해 검토 하였다. Fe의 양이 증가 할 수록 포화자화 값은 증가 하지만 각형비는 감소하였고 보자력도 약간 감소하는 경향을 보였다. Sm(Co0.5Fe0.5)5 조성박막의 경우, 800˚C, 20분 열처리에 의해 약 6.1MGOe의 (BH)max을 보였다. 본 박막자석의 자기적 성질의 증대를 위해서는 시료제작 방법의 개선이 필요하다고 사료 된다.