• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
• /
• pp.1316-1317
• /
• 2006

The paper investigates the possibility to avoid extrinsic embrittlement of $Ni_3Al$, also increasing the high temperature strength, by alloying with both Fe - of a high strengthening effect and Cr - able to remove a part of diffused oxygen along the grain boundaries. As Cr homogenization in $Ni_3Al$ is difficult because of its low diffusion coefficient, for its improving a mechanical alloying (MA) step before the compound synthesis by Self-propagating High-temperature Synthesis (SHS) was adopted. The obtained better homogenization resulted in higher mechanical resistance and deformability than of the unalloyed $Ni_3A/Ni_3Al$ alloys of the same composition obtained without MA step.

• 대한금속재료학회지
• /
• 제50권6호
• /
• pp.463-468
• /
• 2012

A 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ (Mg-23.5Ni-$5Fe_2O_3$) sample was prepared by a quite simple process, reactive mechanical grinding, and its hydriding and dehydriding properties were then investigated. The reactive mechanical grinding of Mg with Ni and $Fe_2O_3$ is considered to facilitate nucleation and shorten the diffusion distances of the hydrogen atoms. After the hydriding-dehydriding cycling, the Mg-23.5Ni-$5Fe_2O_3$ sample contained $Mg_2Ni$ phase. Expansion and contraction of the hydride-forming materials (Mg and $Mg_2Ni$) with the hydriding and dehydriding reactions are also considered to increase the hydriding and dehydriding rates of the mixture by forming defects and cracks leading to the fragmentation of the particles. The temperature dependence of the hydriding rate of the sample is discussed.

• 마이크로전자및패키징학회지
• /
• 제29권4호
• /
• pp.71-75
• /
• 2022

본 연구에서는 환원전극 기판이 철-니켈 합금 도금에 미치는 영향을 알아보기 위해 경면 스테인리스강(SS304, SS430)과 티타늄 판을 환원전극으로 사용해 도금을 진행했으며, 티타늄의 경우 3M 황산-메탄올 용액에서 전압과 연마시간을 조절하여 찾은 최적의 시편(10 V, 8 분)과 표면 처리하지 않은 시편을 사용하였다. 도금층의 조성을 분석한 결과, 스테인리스강과 티타늄 기판에서 니켈보다 환원 경향성이 낮은 철이 먼저 환원되는 비정상 도금 현상이 관찰되었으나 도금층의 앞면과 뒷면의 조성 불균일이 확인되었다. 도금 중 포텐셜 변화를 관찰한 결과, 스테인리스강보다 티타늄을 사용했을 때 도금 셀에 높은 과전압이 걸렸으며, 이로 인해 철의 핵생성 속도가 증가해 과전압이 가장 높았던 표면처리를 하지 않은 티타늄에서 형성된 도금층 뒷면의 철 함량이 높아진 것으로 보인다. 또한 티타늄을 기판을 표면 처리했을 때 셀에 걸린 과전압이 낮아진 것을 확인할 수 있었다.

• 한국수소및신에너지학회논문집
• /
• 제10권1호
• /
• pp.1-7
• /
• 1999

In order to study on the effect of fabrication methods on the changes of hydrogenation properties of FeTi alloy, FeTi samples were prepared using three different methods, i.e., arc melting, mechanical alloying and combination of the two methods. The FeTi prepared by mechanical alloying represented amorphous structure. The hydrogen storage capacity of arc melted FeTi alloy is larger than any other samples. However, FeTi electrode fabricated by mechanical alloying after arc melting showed largest discharge capacity among them.

• 소성∙가공
• /
• 제29권3호
• /
• pp.163-171
• /
• 2020

We present a multi-step cold drawing for a non-equiatomic Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ high entropy alloy (HEA) with a simple face-centered cubic (FCC) crystal structure. The distribution of strain in the cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wires was analyzed by the finite element method (FEM). The effective strain was expected to be higher as it was closer to the surface of the wire. However, the reverse shear strain acted to cause a transition in the shear strain behavior. The critical effective strain at which the shear strain transition behavior is completely shifted was predicted to be 4.75. Severely cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wires up to 96% of the maximum cross-sectional reduction ratio were successfully manufactured without breakage. With the assistance of electron back-scattering diffraction and transmission electron microscope analyses, the abundant deformation twins were found in the region of high effective strain, which is a major strengthening mechanism for the cold-drawn Co₁₀Cr₁₅Fe₂₅Mn₁₀Ni₃₀V₁₀ HEA wire.

• 열처리공학회지
• /
• 제7권1호
• /
• pp.44-52
• /
• 1994

In order to investigate the effect of tempring treatment on the mechanical properties of ausformed martensite in Fe-30%Ni-0.35%C alloy, the hardness, yield strength and elongation were examined by tensile test. 1. The strength of deformed austenite in Fe-30%Ni-0.35%C alloy was increased due to the work hardening induced from the dislocation density increased during deformation. The strength of ausformed martensite was increased because of defects inherited from deformed austenite by martensitic transformation. 2. The ductility of ausformed martensite was shown a nearly constant values independent of deformation degrees because of the interaction of multiple factors such as increased retained austenite, formation of void and decrement of twin in ausformed martensite. 3. The strength of ausformed martensite by tempering treatment was shown a little decrement up to $340^{\circ}C$, especially showed remarkable softening resistance in higher deformation degrees. 4. Virgin martensite and ausformed martensite were shown a maximum yield strength by clustering in tempering at $100^{\circ}C$ and above $100^{\circ}C$, yield strength was very small decreased due to the decrement of solute carbon by the destruction of clustering. 5. The decomposition of retained austenite was not shown up to $450^{\circ}C$ in ausformed martensite with tempering treatment, and the matrix was rapidly softening because of the decomposition of martensite and the formation of reversed austenite with tempering above $400^{\circ}C$.

• 한국자기학회지
• /
• 제5권5호
• /
• pp.543-547
• /
• 1995

A set of $Fe_{1-x}Ni_{x}$ (x=0.10, 0.25, 0.30, 0.35, 0.50, 0.60, 0.75, 0.85) fine particles prepared by the gas evaporation technique was studied by $M\"{o}ssbauer$, XRD and other techniques. The XRD and $M\"{o}ssbauer$ patterns of the sample with x=0.10 ($Fe_{90}Ni_{10}$) were found to be exceptionally different, showing an austenite phase stability when the particles are quenched. This phase stability is quite different from that of the corresponding bulk alloy. Using binomial distrbution fits of the $M\"{o}ssbauer$ spectra of the particles in terms of nearest and next nearest neighbour configurations around the Fe atoms, an analysis of this phase stability is given. The changes in the relative intensities of the resulting magnetic sextets are used to determine the increase in martensite following the austenite-martensite transformation process. The stable austenite can, therefore, be determined. This stability may be related to the oxide surface layer and the small number of atoms of these fine particles.

• Journal of Welding and Joining
• /
• 제18권4호
• /
• pp.96-103
• /
• 2000

This study investigated the effects of bonding temperature and bonding atmosphere on high temperature mechanical properties of transient liquid phase(TLP) bonded joints of heat resistant alloy using MBF-50 insert metal. Specimens were bonded at 1,423~1,468K for 600s. Microconstituents of {TEX}$Cr_{7}(C,B)_{3}${/TEX}were formed in the bonded region when the bonding temperature was low. The amount of microcostituents in the bonded layer decreased with increasing the bonding temperature, and the microconstituents in the bonded layer disappeared at the bonding temperature above 1,468K. The tensile strength of the joints at elevated temperatures increased with the increase the bonding temperature and was the same level as one of the base metal in the bonding temperature over 1,453K. Microstructure and alloying element distributions of the bonded region bonded in Ar and $N_2$atmosphere were similar to those of the bonded in vacuum. The creep rupture strength and rupture lives of joints were almost identical to those of base metal.

• 한국수소및신에너지학회논문집
• /
• 제4권1호
• /
• pp.41-50
• /
• 1993

The hydrogen absorption and desorption characteristics of microencapsulated (CFM)$Ni_{4.7}Al_{0.2}Fe_{0.1}$ and $MmNi_4Fe$ powder with Ni and/or Cu by means of chemical plating method have been investigated. Initial hydrogen absorption rate and activation property were increased remarkably by encapsulation and subsequent compacting. Pellets abtained by compacting of Cu-encapsulated fine powder have fairly good strength even after 30 cycles of hydriding and dehydriding. Encapsulated alloy powder and their compacts show a good resistance to degradation by $O_2$ or CO in hydrogen.

• Journal of Welding and Joining
• /
• 제18권6호
• /
• pp.62-67
• /
• 2000

Metallurgical characteristics of bonded region and high temperature mechanical properties of heat resistant alloy, Fe-35Ni-26Cr during liquid phase diffusion bonding were investigated employing AM17 insert metal. The insert metal for bonding, AM17 was newly developed Ni-base metal using interpolation method. Bonding of specimens were carried out at 1,403~1,463K for 600s in vacuum. The microconstituents in the bonded interlayer disappeared in the bonding temperature over 1,423K. The microstructures, alloying elements and hardness distribution in the base metal. The tensile strength and elongation of the joints at elevated temperatures were the same level as one of the base metal in the bonding temperature over 1,423K. The creep rupture strength and rupture lives of joints were almost identical to those of base metal.