http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
열처리에 따른 니켈기 초내열 713LC 합금의 인장 및 크리프-파단 특성
나영상,박노광,김종엽,염종택 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.11
Microstructure and creep-rupture property of Alloy 713LC were investigated to optimize the utility of Alloy 713LC. The applied heat treatment condition was 1170℃/2hours/air cooling followed by 650℃/16hours/air cooling. During the heat treatment at 1170℃, MC carbide on grain boundary of as-cast Alloy 713LC was partially dissolved and coarsening of γ' particles was contemporaneously taken place so that inhomogeneous distribution in size of γ' particles was observed in heat-treated Alloy 713LC. It was concluded from the high temperature tensile test that the equi-cohesive temperature(ECT) of Alloy 713LC is around 750℃. At higher temperature than ECT, stress-rupture time was not changed after heat treatment. On the other hand, at the temperature around ECT, stress-rupture time decreased by the factor of 10 after heat treatment. This was explained by relating it to the microstructural change of grain boundary and grain interior caused by heat treatment.
동적재료모델에 기초한 초내열 718 합금의 고온 압축변형 거동 해석
나영상,염종택,박노광 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.2
In order to understand more clearly the hot deformation mechanism of Alloy 718 and consequently to determine the "safe" process design window, a number of compression tests were carried out in the range of temperature, 927℃-1066℃ and strain rate, 5×10^-4/s-5/s up to the true strain of 0.7. Based on dynamic materials model, the optimal process design windows, where the deformation is stable, were proposed through the analysis of the constitutive relationships among true stress, true strain, strain rate and temperature. The instability of deformation was confirmed by observing the microstructure of the compression tested samples. Some characteristic microstructures of the localized deformation, such as twinning and shear band, were observed in the samples deformed under the unstable deformation conditions.
고온 압축변형된 니켈기 초내열 718 합금 결정립 조직의 EBSD 분석
나영상,이만형,염종택,박노광 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.3
In order to characterize the dynamic change of microstructures in commercially-available superalloy 718, a series of compression tests were conducted by varying test temperature and strain rate. Orientation relationship and the misorientations between recrystallized grains as well as unrecrystallized grains were thoroughly investigated with EBSD technique. The dynamically-recrystallized grain size was similar regardless of the compression test condition except for the sample tested at 1066℃-0.005/sec condition, where the dynamically-recrystallized grain size was as large as 20 μm in average diameter. In case of the sample tested at 1066℃, flow stress drops caused by the strain softening were almost same at the strain rates of 0.5/sec and 0.005/sec in spite of the different fraction of dynamic recrystallization. It was concluded from the observation of the misorientation angle distribution that it was due to the active dynamic recovery in the unrecrystallized large grains at high temperature. It was also suggested from the variations of CSL boundary distribution that the characteristic redistribution of the dynamically-recrystallized grain boundary might be taken place during the compression at high temperature and low strain rate.