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Cu - Zr 이원계 합금에서 화학조성 및 열싸이클링에 따른 마르텐사이트 특성의 열분석학적 연구
장우양,조민성,이재현,이영수,강조원,곽사호 ( W . Y . Jang,J . Van Humbeerk,M . S . Jo,J . H . Lee,Y . S . Lee,J . W . Kang,S . H . Gwak ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.2
N/A The effects of chemical composition and thermal cycling on the martensitic transformation characteristics in Cu-rich, equiatomic and Zr-rich CuZr binary alloys have been studied by calorimetry. Only martensite could be indentified in equiatomic Cu_(49.9)Zr_(50.1) alloy, while Cu_(10)Zr_7 and CuZr₂intermetallic compounds as well as martensite were formed by rapid cooling from the melts in Cu-rich Cu_(52.2)Zr_(47.5) alloy and Zr-rich Cu_(48.4)Zr_(51.6) alloy, respectively. The M_s temperature of Cu_(49.9)Zr_(50.1) was 156℃ but those of Cu_(52.5)Zr_(47.5) and Cu_(48.4)Zr_(51.6) alloys, being 109℃ and 138℃, were lower than that of equiatomic Cu_(49.9)Zr_(50.1) alloy. In all the alloys, the M_s temperature has fallen but the A_s temperature has risen, resulting in widening of the transformation hysteresis with thermal cycling. The anomalous characteristics in the transformation temperature are due to the presence of the intermetallic compounds i.e. Cu_(10)Zr_7 and CuZr₂formed by an eutectoid reaction during thermal cycling in the temperature range between -100℃<T_c<400℃.
논문 : 상변태 ; Fe-32Mn-6.5Si 합금에서 형상기억효과 및 변태거동에 미치는 미세조직의 영향
이지영 ( J. Y. Lee ),지광구 ( K. K. Jee ),최종술 ( C. S. Choi ),장우양 ( W. Y. Jang ),신명철 ( M. C. Shin ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.6
The objective of this study is to investigate the effect of microstructure and pre-strain on shape memory effect(SME) and transformation behavior in an Fe-32Mn-6.5Si alloy. The alloy was annealed at various temperatures from 600 to 1200℃ for 1 hour to vary microstructure after cold rolling. Shape memory effect and reverse transformation behavior were examined through bending test and TMA after deforming the alloy with various degrees of pre strain Austenite grain size increases with an increase in heat treatment temperature, except the specimen heat-treated at 600℃, which remains unrecrystallized. The specimen heat-treated at 600℃, retaining cold rolling effect, exhibits the best SME due to a high Md temperature. In the recrystallized specimens, the larger grain size, the better SME. As grain size increases, the reverse transformation range becomes shorter, indicating that reverse transformation takes place with less constraint. The better SME in a large grain size can be attributed to the easiness of the reverse transformation.
Fe - X%Mn - 5Cr - 5Co - 4Si 합금 리본의 변태특성 및 형상기억능에 미치는 열처리 영향
강후원(H . W . Kang),지광구(K . K . Jee),장우양(W . Y . Jang),강조원(J . W . Kang) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.3
N/A The change of ribbon geometry, microstructure and shape recovery with Mn contents, wheel speed and various annealing temperature have been studied in Fe-X%Mn-5Cr-5Co-4Si(X%=15, 20, 24) shape memory alloy (SMA) ribbons rapidly solidfied by single roll chill-block melt-spinning process. The thickness and width of melt-spun ribbons are reduced, results in refining and uniformalizing grains with increasing wheel speed. In the ribbons melt-spun at a wheel speed of 15m/sec, both a and α`martensites are formed in ribbon 1 (15.5wt%Mn), while only ε martensite is revealed in ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn). The volume fraction of a martensite is decreased with increasing Mn contents, and those of ε as well α`martensites are increased due to thermal stress relief and grain growth with increasing annealing temperature. Mn temperatures of the ribbons 1, 2 and 3 are fallen with increasing Mn contents. M_s temperatures of the ribbons 1, 2 and 3 annealed at 300℃ for 3min are risen abruptly, but are nearly constant even at higher annealing temperature, i.e., 400, 500 and 600℃ for 3 min. Shape recovery of the ribbons 1, 2 and 3 increased 30%, 52% and 69% with Mn contents, respectively. Shape recovery of ribbon 1 (15.5wt%Mn) formed ε and α`martensites decreased because of the presence of α`martensite but those of ribbon 2 (20.2wt%Mn) and ribbon 3 (23.5wt%Mn) formed ε martensite increased with increasing annealing temperature.
결정립 미세화된 Cu-Zn-Al 형상기억합금의 열처리 조건에 따른 변태거동
강조원,장우양,양권승 ( J . W . Kang,W . Y . Jang,G . S . Yang ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.4
A small amount of misch metal and/or Zr was added as a dopant to 70.5wt%Cu-26wt%Zn-3.5wt%Al shape memory alloy in order to study the effect of grain refinement and heat treatments on the transformation behavior, stabilization of martensite, and shape memory ability. It was found that the addition of misch metal and Zr was very effective for reducing the grain size. The fracture mode has been changed from intergranular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal and Zr. Aging of the β-phase decreases the M_5 temperature, but that of the martensite phase increases the A_s temperature. The hysteresis of transformation temperature ΔT(A_s-M_s) has an increasing tendancy by grain refinement. The crystal structure of martensite was identified as monoclinic structure. As the grain size decreased, martensite stabilization more easily occured and the shape, memory ability has been reduced by the grain size refined.
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℃.
TRIP형 복합조직강의 미세조직 및 인장성질에 미치는 화학조성의 영향
이기열 ( K. Y. Lee ),장우양 ( W. Y. Jang ),강조원 ( J. W. Kang ) 한국열처리공학회 2003 熱處理工學會誌 Vol.16 No.3
N/A The effect of chemical composition on the microstructural change and tensile property in TRIP-assisted steels with different chemical composition was investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite could be identified as two types: a granular type in a steel containing higher Si and a film type in a steel having higher C. For the case of higher C-containing steel with a tensile strength of 860 MPa and a total elongation of 38%, film-typed retained austenite could be observed between lath bainitic ferrite. Actually, metastable retained austenite was a requisite for the good formability, which means that chemical composition plays a significant role in the microstructure and tensile property of TRIP-assisted steels. With respect to tensile property, the steels containing suitable Si and Mn, respectively, showed a typical TRIP effect in stress-strain curve, while a steel containing higher Mn content exhibited the similar behavior shown in dual phase steel.