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주조 합금 Alloy 718에서 미세조직과 인장특성에 미치는 열처리의 영향
도정현 ( Jeong-hyeon Do ),김인수 ( In-soo Kim ),최백규 ( Baig-gyu Choi ),정중은 ( Joong-eun Jung ),정인용 ( In-yong Jung ),조창용 ( Chang-yong Jo ) 한국주조공학회 2016 한국주조공학회지 Vol.36 No.5
The effect of various types of heat-treatment on the mechanical properties of cast Alloy 718 has been investigated. Cast Alloy 718 bars were subjected to ‘standard heat-treatment`_(SHT), ‘HIP (Hot Isostatic Pressing) heat-treatment`_(HHT), and ‘HIP-sim-ulated heat-treatment`_(HS). In the absence of long time high temperature heat-treatment, a small amount of Laves phase remained in the ‘SHT` specimen, and needle shaped δ precipitated in the vicinity of the Laves phase. Due to the formation of the Laves and δ phases in the ‘SHT` specimen, it exhibited lower tensile properties than those of the others_specimens. On the other hand, the Laves phase was completely dissolved into the matrix after ‘HHT` and ‘HS` treatments. It is known that isostatic pressure reduces the self-diffusion coefficient, because of the lower self-diffusivity under HIP conditions in the interdendritic region, Nb segregation and the high amount of γ” precipitation that occurs. Due to the higher fraction of coarse γ” phases, the ‘HHT` treated Alloy 718 showed excellent tensile strength.
Comparative analysis of US and China artificial intelligence patents trends
Daejung Kim(김대중),Joong-Hyeon Jeong(정중현),Hokyoung Ryu(류호경),Jieun Kim(김지은) 한국컴퓨터정보학회 2019 韓國컴퓨터情報學會論文誌 Vol.24 No.1
With the rapid development of artificial intelligence technology, the patenting activities related to the fields of AI is increasing worldwide. In particular, a share of patent filed in China has exploded in recent years and overtakes the numbers in the US. In the present study, we focus our attention on the patenting activity of China and the US. We analyzed 6,281 and 13,664 patent applications in the US and China respectively between 2008 and 2018, and belonging to the “G06F(Electric Digital Data Processing)”, “G06N(Computer Systems Based on Specific Computational Models)”, “H04L(Transmission of Digital Information)” and nine more relevant technological classes, as indicated by the International Patent Classification(IPC). Our analysis contributes to: first, the understanding of patent application trends from foreign countries filed in the US and China, 2) patent application status by applicants category such as companies, universities and individuals, 3) the development direction and forecasting vacant technology of AI according to main IPC code. Through the analysis of this paper, we can suggest some implications for patent research related to artificial intelligence in Korea. Plus, by analyzing the most recent patent data, we can provide important information for future artificial intelligence technology research.
니켈기 초내열합금의 열간노출에 따른 미세조직 및 기계적 특성 변화
김인수 ( In-soo Kim ),최백규 ( Baig-gyu Choi ),정중은 ( Joong-eun Jung ),도정현 ( Jeong-hyeon Do ),정인용 ( In-yong Jung ),조창용 ( Chang-yong Jo ) 한국주조공학회 2016 한국주조공학회지 Vol.36 No.5
The microstructural evolution of a cast Ni base superalloy, IN738LC, has been investigated after long term exposure at several temperatures. Most of the fine secondary γ` particles resolved after 2000 hour exposure at 816℃. At higher temperatures of 871℃ and 927℃, secondary γ` resolved after 1000 hours of exposure, and cuboidal primary γ` grew with exposure time. During the ther-mal exposure, σ phase formed at all tested temperatures, and η phase was observed around interdendritic regions due to carbide degeneration. The influence of microstructural evolution during thermal exposure on the mechanical properties has been analyzed. The effects of γ` particle growth are more pronounced on the high temperature creep properties than on the room temperature tensile properties.
니켈기 초내열 합금 GTD 111에서 편석에 의한 합금원소 분포 및 미세조직 변화
최백규 ( Baig Gyu Choi ),김인수 ( In Soo Kim ),도정현 ( Jeong Hyeon Do ),정중은 ( Joong Eun Jung ),조창용 ( Chang Yong Jo ) 한국주조공학회 2015 한국주조공학회지 Vol.35 No.6
Segregation during solidification and homogenization during thermal exposure in GTD 111 were investigated. The microstructures of as-cast, standard heat-treated, and thermally exposed specimens were observed by SEM. A compositional analysis of each specimen was conducted by EDS. The dendrite core was enriched in W and Co, though lower levels of Ti and Ta were observed. An unexpected phase, in this case like the η phase, was observed due to segregation near the γ-γ`` eutectic in the standard heat-treated specimen. Segregation also induced microstructural evolution near the γ-γ`` eutectic during the standard heat treatment. A quantitative analysis and microstructural observations showed that the thermal exposure at a high temperature enhanced the chemical homogeneity of the alloy.