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Fe-Mn계 합금에서 응력유기 ε 마르텐사이트의 양에 미치는 열처리 온도의 영향
지광구 ( K. K. Jee ),한주현 ( J. H. Han ),장우양 ( W. Y. Jang ) 한국열처리공학회 2004 熱處理工學會誌 Vol.17 No.6
N/A In this work, a new method of measuring volume fraction of deformation-induced ε martensite is pro-posed using endothermic heat on reverse transformation. As grain size increases, the amount of ε martensite forming on cooling increases. However, with a decrease in grain size, more ε is induced by deformation, improving shape memory effect.
Ni-Al 계 마르텐사이트 합금에서 Llo → Ni5Al3 변태
지광구(K. K. Jee),송시연(S. Y. Song),장우양(W. Y. Jang) 한국열처리공학회 2002 熱處理工學會誌 Vol.15 No.2
N/A LI_0 → Ni_5Al_3 reordering and related properties in Ni-Al alloys consisting of 64-65at%Ni are characterized by X-ray diffraction, shape memory effect and damping capacity. Formation of Ni_5Al_3 takes place by simple ordering of atoms with a continuous increase in c/a ratio. As a result, degradation of shape memory effect and damping capacity is observed after short time annealing at 200-300℃.
Fe-Mn 계 합금에서 비부피 차를 이용한 ε 마르텐사이트의 부피분율 측정
지광구 ( Ji Gwang Gu ),한준현 ( Han Jun Hyeon ),장우양 ( Jang U Yang ) 한국열처리공학회 2003 熱處理工學會誌 Vol.16 No.4
N/A In this work, a new way of measuring the volume fraction of E martensite in Fe-based alloys has been proposed. Since the specific volume of ε martensite, depending on alloy composition, is smaller than that of austenite i.e γ phase, volume expansion takes place during ε→γ reverse transformation. As the amount of the volume expansion is proportional to the product of specific volume difference times the volume fraction of ε martensite, the volume fraction of ε martensite can be calculated by measuring the volume expansion and the specific volume difference. Such a relationship was confirmed in Fe-21 Mn and Fe-32Mn-6Si alloys which undergo γ→ε martensitic transformation on cooling and by cold rolling, respectively. It was also found that the former has isotropic E martensite while the latter has anisotropic E martensite.
신명철,지광구,한준현,미서군 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.1
Temperature response is tested for a Ni-Ti shape memory spring with prestrain or a constant load. An apparatus for measuring variation in deflection of the spring with temperature and DSC are employed to evaluate the characteristics. Localized elastic stress, accumulating on thermo-mechanical cycling, give rise to excess recovery, i.e., continuance of shape change at temperatures well above Af. The accumulation of even apparently elastic stress concentration can initiate dislocation slip, causing a SMA spring to lose its precision. Thus it is strongly advised that SMA thermo-actuator be cycled until no further permanent is induced, before its parameters are evaluated for designing.
신명철,지광구,P.L.포타포프,송시연 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.9
Energetistic consideration of shape memory alloys(SMAs) is carried out in this work. ΔW_(cri), a criterion of energy, is developed to characterize and evaluate intrinsic property of a SMA. Through an experiment with Mn-Cu SMA, ΔW_(cir) is measured for a spiral and a spring and their efficiency is discussed by calculating their geometry factors.
Fe-7%Ni-0.4%C 마르텐사이트합금의 미세조직과 진동감쇠능에 미치는 용체화처리온도의 영향
이영국,지광구,최종술 ( Young Kook Lee,Kwang Koo Jee,Chong Sool Choi ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.1
The objective of this study is to investigate the effect of solution-treatment temperature on the microstructure and damping capacity of a martensitic Fe-7%Ni-0.4%C alloy. The size of lath increased from 0.3㎛ to 0.55㎛ with increasing the solution-treatment temperature from 700 to 1100℃. In addition, the size of block, packet, and austenite grain had tendency to increase with increasing solution-treatment temperature. The damping capacity of the Fe-7%Ni-0.4%C martensitic alloy decreased with increasing the solution treatment temperature. The reason is not attributed to the increase in the size of lath, block, packet, and austenite grain, but to the increase in vacancy concentration which hinders dislocation motion.