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Hydrogen permeation characteristics of rolled V85Al10Co5 alloys
에릭플러리,서진유,김동익,정찬훈,박정훈 한국물리학회 2012 Current Applied Physics Vol.12 No.4
Thin sheets of V85Al10Co5 alloy were produced by a thermo-mechanical treatment consisting in successive hot rolling, cold rolling steps and annealing treatment at high temperature followed by either air cooling or water quenching. Though the values of hydrogen permeability measured for these sheets were significantly reduced as a consequence of the rolling process, the annealing treatment restored almost the hydrogen permeation properties to those of the alloy in the cast condition. EBSD analyses suggested that the post-annealing treatment performed at 1100 ℃ for 3 min after cold rolling induced a recrystallization of the grains resulting in a preferred orientation along the {002} planes. For the sample annealed and water quenched, the value of the hydrogen flux reached about 45 ml/cm2.min, which is more than twice the value of the flux obtained for thin foils of Pd alloys tested under identical conditions.
오지윤,서진유,김우진,장재일,강기훈,윤종승,임혜인 한국물리학회 2018 Current Applied Physics Vol.18 No.4
The viscous thermal flow behavior and mechanical property of [Fe0.6Co0.15B0.2Si0.05] (100−x)Tax (x = 0, 1, 2, 3, 4, and 5) soft magnetic amorphous ribbons were studied. The characteristics of melt-spun amorphous ribbons were measured by using vibration sample magnetometer (VSM), nanoindentation, differential scanning calorimetry (DSC) and thermo-mechanical analysis (TMA) to study the effects of Ta content variation on the thermal stability, mechanical, and soft magnetic properties. We observed that the nanoindentation hardness, Young's modulus, and glass transition and crystallization temperatures were improved by the addition of Ta. Using dilatometry measurement, TMA, by heating at a constant rate under tension mode, we examined not only the glass transition and crystallization behaviors but also the possibility of coexistence of multiple amorphous phases.
압연에 의한 STS/AI/STS 클래드판재 제조시 롤과 STS 사이의 마찰의 영향
정영훈,지광구,서진유,신명철 한국소성가공학회 2002 소성가공 : 한국소성가공학회지 Vol.11 No.6
Sandwich sheets composed of stainless steel/aluminum/stainless steel were produced by roll cladding. In order to investigate the effect of the friction between roll and cladding sample, the lubrication condition of the roll surface was varied. Clad rolling without lubrication gave rise to a small increment of the normal strain of aluminum in the rolling direction. This experimental result was confirmed by FEM modeling. Through-thickness hardness gradients in the mid aluminum layer was successfully explained by variations of the strain state through thickness layers. FEM modeling implied that cladding without lubrication led to a large shear strain variation at the surface of aluminum layer.
김지혜,김수민,서진유,김용진,김영근,임혜인 한국물리학회 2019 Current Applied Physics Vol.19 No.4
The rare-earth-free hard magnetic L10-FeNi phase found in cosmic meteorites demonstrates potential as a nextgeneration permanent magnet. However, it is very difficult to artificially produce the L10-FeNi phase due to the low atomic diffusion coefficients of Fe and Ni near the order-disorder transition temperature (∼320 °C). Therefore, FeNiPC amorphous alloy systems exhibiting crystallization temperature (Tx) near the transition temperature were investigated. The amorphous alloys were annealed at Tx, resulting in high atomic diffusion. The structural and microstructural characterizations of annealed ribbons revealed the formation of L10-FeNi phase through observation of the superlattice peak. The magnetic property, such as coercivity (Hc), also indicated the formation of L10-FeNi phase, because the maximum Hc value is 641 Oe after the annealing process.
Equal-Channel Angular Pressing 에서의 변형거동해석
김희수,박종우,서진유 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.9
Numerical and experimental studies of equal-channel angular pressing was carried out to verify theoretical deformation models. Finite element method was used to calculate the grid deformation and the effective plastic strain field with various die shapes. When the curvature angle is zero, a homogeneous shear deformation occurs on the cross section of the specimen, which is well predicted by the theoretical models. As the curvature angle increases, the shear deformation is found to be comparatively uniform at the upper part of the specimen, and the effective plastic strain is in a good agreement with the theoretical value. However, the shear deformation at the lower part of the specimen becomes smaller, and the effective plastic strain is considerably different from the theoretical result. Model experiments using plexiglass molds and plasticine billets supported well with the results of the finite element analysis.