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Fe-29%Ni-17%Co 저열팽창 합금의 열팽창 특성에 미치는 냉간 가공 및 열처리의 영향
이기안 ( Kee Ahn Lee ),권진한 ( Jin Han Gwon ),박종혁 ( Jong Hyuk Park ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.1
The changes to thermal expansion and mechanical properties by cold working were investigated in the Fe-29%Ni-17%Co (wt%) low thermal expansion alloy. The Fe-29%Ni-17%Co alloy was cold rolled gradually and prepared for plating with reduction ratios of 0%, 20%, 40%, 60%, and 80%. The effect of annealing on the property was also studied. Thermal expansion was measured from 25 ℃ to 600 ℃ using a vacuum differential dilatometer. We found that the thermal expansion coefficient (α30~400) slightly decreased (at a reduction ratio of 20%) and then remarkably increased (above reduction ratios of 40%) with increasing reduction ratios of cold rolling. The thermal expansion coefficient (α30~400) sharply decreased after heat treatment. Yield and tensile strengths continuously increased and elongation decreased by cold rolling. Microstructural observation and XRD analysis results showed that the α phase significantly increased as the reduction ratio increased. The slight decrease of the thermal expansion coefficient below a reduction ratio of 20% could be explained by the destruction of short-range ordering and decrease in grain size. The significant increase in the thermal expansion coefficient with cold rolling attributed to the appearance of the α phase. The correlation between the microstructural cause and invar effect of the low thermal expansion behavior is also discussed. (Received April 7, 2014)
Kinetic Spray 공정으로 제조된 Nb 코팅 소재의 미세조직 및 물성에 미치는 열간 등압 성형(HIP)의 영향
이지혜,양상선,이기안,Lee, Ji-Hye,Yang, Sangsun,Lee, Kee-Ahn 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.1
Niobium is one of the most important and rarest metals, and is used in the electronic and energy industries. However, it's extremely high melting point and oxygen affinity limits the manufacture of Nb coating materials. Here, a Nb coating material is manufactured using a kinetic spray process followed by hot isotactic pressing to improve its properties. OM (optical microscope), XRD (X-ray diffraction), SEM (scanning electron microscopy), and Vickers hardness and EPMA (electron probe micro analyzer) tests are employed to investigate the macroscopic properties of the manufactured Nb materials. The powder used to manufacture the material has angular-shaped particles with an average particle size of $23.8{\mu}m$. The porosity and hardness of the manufactured Nb material are 0.18% and 221 Hv, respectively. Additional HIP is applied to the manufactured Nb material for 4 h under an Ar atmosphere after which the porosity decreases to 0.08% and the hardness increases to 253 Hv. Phase analysis after the HIP shows the presence of only pure Nb. The study also discusses the possibility of using the manufactured Nb material as a sputtering target.
Kinetic Spray 공정으로 제조된 탄탈륨 코팅층의 열처리 분위기에 따른 미세조직 및 물성
이지혜,김형준,이기안,Lee, Ji-Hye,Kim, Hyung-Jun,Lee, Kee-Ahn 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.1
The effect of heat treatment environment on the microstructure and properties of tantalum coating layer manufactured by kinetic spraying was examined. Heat treatments are conducted for one hour at $800^{\circ}C$, $900^{\circ}C$, and $1000^{\circ}C$ in two different environments of vacuum and Ar gas. Evaluation of microstructure and physical properties are conducted. High density ${\alpha}$-tantalum single phase coating layer with a porosity of 0.04% and hardness of 550 Hv can be obtained. As heat treatment temperature increases, porosity identically decreases regardless of heat treatment environment (vacuum and Ar gas). Hardness of heat treated coating layer especially in Ar gas environment deceases from 550 Hv to 490 Hv with increasing heat treatment temperature. That in vacuum environment deceases from 550 Hv to 530 Hv. The boundary between particles became vague as heat treatment temperature increases. Oxygen distribution of tantalum coating layer is minute after heat treatment in vacuum environment than Ar gas environment.