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고온에서 미세입자를 가진 석출경화형 Al-0.55wt% Zr 합금의 Thershold 응력과 전위/입자의 상호 작용에 관한 연구)
김병일,중도영치 ( Byubg I Kim,Hideharu Nakashima ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.4
An experimental study of the constitutive response of precipitation-strengthened Al-0.55wt% Zr alloy, which consists of an Al matrix precipitation-strengthened by coherent particles, β`(Al₃Zr) with Ll₂ structure has been performed. The deformation response of the materials has been examined by stress relaxation test at 573K, 623K and 673K. It was found that there exist the threshold stress during stress relaxation and threshold stress results from the presense of β`(Al₃Zr) particles. The ratio of threshlod stress and Orowan stress decreased gradually with increasing temperature. The resistance to climb-pass of particles was independent of particles size for a fixed volume fraction although the threshold for bowing and particles cutting are sensitive to the particles dimensions. The smaller particles cutted by dislocations. This behavior of dislocations in this alloy was explained in terms of the small value antiphase boundary energy. The dislocation networks wrere more extensive in spesimens subjected to stress relaxation and there were numerous areas that have a high denstiy of jogged dislocation. This experiment results indicate that the rate controlling stress relaxation process is the climb of edge disloaction over particles.
Al-Mg-Mn 합금의 고온 연성 저하에 미치는 분산입자의 효과
김병일,중도영치,길전동수,길영불남 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.9
The dependency of the ductility of Al-Mg-Mn alloy containing Al_6Mn particles on temperature and strain rate was examined by using standard tensile test. The ductility minimum was found to be at 773K for 2.7×10^(-3), 5.5×10^(-3) and 1.1×10^(-2) strain rates, and the reduction of area decreased with increasing temperature 'irrespective of strain rates. The rate of ductility loss increased significantly at lower strain rate and at higher temperature. However, the maximum ductility drop occurred at the same temperature, 773K, for various strain rates. For 2.7×10^(-3) and 5.5×10^(-3) strain rates, ductility was determined uniquely by the parameter Z=ε˙ exp(Q/RT) at Z= ≥10^6s^(-1). Brittle fracture showing the ductility loss at higher temperature was associated with cavity growth as well as interlinkage of cavities, while a number of dimples were observed on the fracture surface at lower temperatures.
논문 : 기계적 성질 ; Al-Mg-Be 합금의 고온 연성저하 현상
김병일 ( Byung Il Kim ),길전동수 ( Fuyuki Yoshida ),중도영치 ( Hideharu Nakashima ),길영일출남 ( Hideo Yoshinaga ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.6
The high temperature ductility behaviors of Al-Mg-Be alloy containg particles in grain have been studied using a tensile test and scanning electron microscopy. The results show that the reduction of area increased with increasing temperature up to 523K and the minimum ductility was found to be at 573K for 8.3 × 10-5s-1 strain rate. The rate of ductility loss of the Al-Mg-Be alloy deformed at 573K under strain rate, 8.3 × 10-4s-1 was higher than that of under a strain rate, 8.3 × 10-5s-1 However, the maximum ductility drop was occured at the same temperature, 573K for various strain rate. The reduction of area was not determined uniqely by Zenner-Hollomon parameter, Z=εexp(Q/RT). The cleavage fracture showing the ductility loss at higher temperature was associated with cavity growth as well as interlinkage of cavities. On the other hand, ductile fracture was observed on the fracture surface at lower temperature.