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레이저 직접 용착공정으로 형성된 스테인레스/인코넬 합금 계면의 미세조직 분석
엄영성,김경태,정수호,유지훈,양동열,최중호,심철용,안승준,Eom, Yeong Seong,Kim, Kyung Tae,Jung, Soo-Ho,Yu, Jihun,Yang, Dong Yeol,Choe, Jungho,Sim, Chul Yong,An, Seung Jun 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.3
The directed energy deposition (DED) process of metal 3D printing technologies has been treated as an effective method for welding, repairing, and even 3-dimensional building of machinery parts. In this study, stainless steel 316L (STS316L) and Inconel 625 (IN625) alloy powders are additively manufactured using the DED process, and the microstructure of the fabricated STS316L/IN625 sample is investigated. In particular, there are no secondary phases in the interface between STS316L and the IN625 alloy. The EDS and Vickers hardness results clearly show compositionally and mechanically transient layers a few tens of micrometers in thickness. Interestingly, several cracks are only observed in the STS 316L rather than in the IN625 alloy near the interface. In addition, small-sized voids 200-400 nm in diameter that look like trapped pores are present in both materials. The cracks present near the interface are formed by tensile stress in STS316L caused by the difference in the CTE (coefficient of thermal expansion) between the two materials during the DED process. These results can provide fundamental information for the fabrication of machinery parts that require joining of two materials, such as valves.
선택적 레이저 용융공정으로 제조된 Al-Si-Mg 합금의 열처리에 따른 미세조직 및 특성평가
이기승,엄영성,김경태,김병기,유지훈,Lee, Gi Seung,Eom, Yeong Seong,Kim, Kyung Tae,Kim, Byoung Kee,Yu, Ji Hun 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.2
In this study, Al-Si-Mg alloys are additively manufactured using a selective laser melting (SLM) process from AlSi10Mg powders prepared from a gas-atomization process. The processing parameters such as laser scan speed and laser power are investigated for 3D printing of Al-Si-Mg alloys. The laser scan speeds vary from 100 to 2000 mm/s at the laser power of 180 and 270 W, respectively, to achieve optimized densification of the Al-Si-Mg alloy. It is observed that the relative density of the Al-Si-Mg alloy reaches a peak value of 99% at 1600 mm/s for 180 W and at 2000 mm/s for 270W. The surface morphologies of the both Al-Si-Mg alloy samples at these conditions show significantly reduced porosities compared to those of other samples. The increase in hardness of as-built Al-Si-Mg alloy with increasing scan speed and laser power is analyzed due to high relative density. Furthermore, it was found that cooling conditions after the heat-treatment for homogenization results in the change of dispersion status of Si phases in the Al-Si matrix but also affects tensile behaviors of Al-Si-Mg alloys. These results indicate that combination between SLM processing parameters and post-heat treatment should be considered a key factor to achieve optimized Al-Si alloy performance.