http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
고에너지 직접 적층법으로 제조된 경사조성재료의 미세조직 및 경도 변화에 미치는 후열처리 영향 연구
신기승,박용호,김대환,윤지현,김정한 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.2
In this work, the effects of post weld heat treatment (PWHT) on the microstructure and mechanical properties of functionally gradient materials (FGM) was investigated. The FGM consisted of five different layers which were mixtures of austenitic stainless steel (type 316L) and ferritic steel (LAS). The ratio of type 316L and LAS powder in each deposition layer was 100:0, 75:25, 50:50, 25:75, and 0:100. FGM samples were successfully fabricated without cracks or delamination by a direct energy deposition process. The sensitization phenomenon of the FGM samples was investigated after PWHT. The PWHTs were conducted at 700 oC, 900 oC, and 1100 oC for 4 hours and the samples were then air-cooled. After PWHT, the annealed specimens were observed by optical and scanning electron microscopy to analyze their microstructure. The occurrence of sensitization was found in the specimen annealed at 700 oC. The contents of Cr and C increased substantially along grain boundaries. However, the sensitization did not occur in other samples annealed at 900 oC and 1100 oC. In the C and D layers of the 1100 oC annealed sample, micro-hardness was measured to be very high due to the formation of bainitic ferrite and a lath martensite structure. In addition, a reduction of the austenite fraction was confirmed by Electron Back Scatter Diffraction.
Ti-10wt.%Al-xMn 분말합금의 Mn첨가에 따른 소결특성 평가
신기승,현용택,박노광,박용호,이동근,Shin, Gi-Seung,Hyun, Yong-Taek,Park, Nho-Kwang,Park, Yong-Ho,Lee, Dong-Geun 한국분말야금학회 2017 한국분말재료학회지 (KPMI) Vol.24 No.3
Titanium alloys have high specific strength, excellent corrosion and wear resistance, as well as high heat-resistant strength compared to conventional steel materials. As intermetallic compounds based on Ti, TiAl alloys are becoming increasingly popular in the aerospace field because these alloys have low density and high creep properties. In spite of those advantages, the low ductility at room temperature and difficult machining performance of TiAl and $Ti_3Al$ materials has limited their potential applications. Titanium powder can be used in such cases for weight and cost reduction. Herein, pre-forms of Ti-Al-xMn powder alloys are fabricated by compression forming. In this process, Ti powder is added to Al and Mn powders and compressed, and the resulting mixture is subjected to various sintering temperature and holding times. The density of the powder-sintered specimens is measured and evaluated by correlation with phase formation, Mn addition, Kirkendall void, etc. Strong Al-Mn reactions can restrain Kirkendall void formation in Ti-Al-xMn powder alloys and result in increased density of the powder alloys. The effect of Al-Mn reactions and microstructural changes as well as Mn addition on the high-temperature compression properties are also analyzed for the Ti-Al-xMn powder alloys.
DED 공정으로 제조된 경사조성재료 (STS 316L과 저합금강)의 미세조직 및 기계적특성 평가
신기승,추웅,윤지현,양승용,김정한 한국분말재료학회 2022 한국분말재료학회지 (KPMI) Vol.29 No.4
In this study, additive manufacturing of a functionally graded material (FGM) as an alternative to joining dissimilar metals is investigated using directed energy deposition (DED). FGM consists of five different layers, which are mixtures of austenitic stainless steel (type 316 L) and low-alloy steel (LAS, ferritic steel) at ratios of 100:0 (A layer), 75:25 (B layer), 50:50 (C layer), 25:75 (D layer), and 0:100 (E layer), respectively, in each deposition layer. The FGM samples are successfully fabricated without cracks or delamination using the DED method, and specimens are characterized using optical and scanning electron microscopy to monitor their microstructures. In layers C and D of the sample, the tensile strength is determined to be very high owing to the formation of ferrite and martensite structures. However, the elongation is high in layers A and B, which contain a large fraction of austenite.
Ti-6AI-4V 판재를 이용한 사각형 컵 열간 딥 드로잉 성형
신기승(G. S. Shin),박진기(J. G. Park),김영석(Y. S. Kim),박노광(N. K. Park) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.10
In the last decades, the usage of titanium alloys in aircraft components is gradually increasing. In this research, deep drawing of 200x200mm square cup was investigated to establish fundamental understanding on the sheet forming of Ti-6Al-4V alloy. For this purpose, FE-simulation(Abaque code) was performed to determine optimum size, punch speed, blank size, the gap between punch and die, and etc. The acquired processing parameters were verified experimentally. Based on the FE-simulation results, deep drawing was performed with various load and sample sizes. In order to improve the formability of alloys, various lubricant methods were introduced. After forming, tensile tests and thickness measurement were carried out prior to the pickling, lubricants, and optimum blank size, were considered to improve forming quality. Using the optimum processing condition, 200mmx200mm cup drawing was performed successfully.