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임성혁,임종국,김경환,최재하 ( S . H . Im,S . K . Rhim,K . H . Kim,J . H . Choi ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.3
The-steady-state creep mechanism and behavior of Zircaloy-4 used as cladding materials in PWR have been investigated in air environment over the temp. ranges from 600 to 645℃ and stress ranges from 4 to 7㎏/㎟. The stress exponents for the creep deformation of this alloy, n were decreased 4.81, 4.71, 4.64, and 4.56 at 600, 615, 630 and 645℃, respectively; the stress exponents decreased with increasing the temperature and got closer to about 5. The apparent activation energies, Q, were 62.1, 60.0, 57.9 and 55.4 ㎉/mole at stresses of 4, 5, 6, 7㎏/㎟, respectively; the activation energies decreased with increasing the stress and were close to those of volume self diffusion of Zr in Zr-Sn-Fe-Cr system. In results, it can be considered that the creep deformation for Zircaloy-4 was controlled by the dislocation climb over the ranges of this experimental conditions. Larson-Miller parameter, P, for the crept specimens was obtained as P=(T+460)(logt_r+23). The failure plane observed by SEM slightly showed up intergranular fracture at this experiment ranges. However, it was essentially dominated by the dimple phenomenon, which was a characteristics of the transgranular fracture.
박규철(K . C . Park),김경환(G . H . Kim),문준영(J . Y . Mun),최재하(J . H . Choi) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.4
N/A The static creep behaviors of dispersion strengthened copper GlidCop were investigated over the temperature range of 650∼690℃(0.7Tm) and the stress range of 40∼55 ㎫ (4.077∼5.61㎏/㎟). The stress exponents for the static creep deformation of this alloy was 8.42, 9.01, 9.25, 9.66 at the temperature of 690, 677, 663, and 650℃, respectively. The stress exponent, (n) increased with decreasing they temperature and became close to 10. The apparent activation energy for the static creep deformation, (Q) was 374.79, 368.06, 361.83, and 357.61㎏/mole for the stress of 40, 45, 50, and 55 ㎫, respectively. The activation energy (Q) deceased with increasing the stress and was higher than that of self diffusion of Cu in the dispersion strengthened copper. In results, it can be concluded that the static creep deformation for dispersion strengthened copper was controlled by the dislocation climb over the ranges of the experimental conditions. Larson-Miller parameter (P) for the crept specimens for dispersion strengthened copper under the static creep conditions was obtained as P=(T+460)(logtr+23). The failure plane observed for SEM slightly showed up transgranular at that experimental range, however, universally it was dominated by characteristic of the intergranular fracture.
Cyclic Reverse Double Shear Creep 시 초소성 Zn-22% Al 합금의 결정립 성장에 관한 연구
지태구,송태석,최재하,조형호,김명한 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.3
The cyclic reverse double shear creep test was adopted to investigate the grain growth of Zn-22% Al superplastic alloy. The results represent that the shear specimens experience more increment of concurrent grain growth and consequently increase in grain size, as the test cycle increases. The results indicate that stress reversal effect is the major factor influencing grain growth in shear test. The relation between shear strain rate(γ˙) and grain size (d) could be expressed as follow, when the unit of γ˙ and d is 10-⁴/sec and ㎛, respectively : log γ˙=-1.2571og d-3.7