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CuAlNi 형상기억합금의 시효처리에 따른 상변태 거동
양권승,강조원 ( G . S . Yang,J . W . Kang ) 한국열처리공학회 1993 熱處理工學會誌 Vol.6 No.4
This research was performed to investigate the transformation behavior and shape memory effect of Cu13.5Al-4.5Ni(wt%) alloy with various aging temperature and time. The results obtained in this study are as follows: Transformation temperature was very increased when aging temperature is at 250℃. The variation of transformation temperature in first reverse transformation cycle and second was very significant, but there was little difference in case of 2nd and 3rd, Transformation temperature at various aging temperature was increased with increasing of aging temperature and time. Microvickers hardness was increased with increasing of aging temperature and time. It was found that α and γ₂phase were created by aging of long time at high 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.
Cu-Al-Ni-Ti-Mn 합금의 변태특성 및 기계적 성질에 미치는 가공열처리의 영향
강조원,장우양,양권승,이영수,곽사호,김춘동,백승남 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.2
The distribution of the second phase, the change of transformation temperature and mechanical properties with thermomechanical treatment conditions were investigated by metallography, calorimetry, EDS, tensile test and fractography in a Cu-Al-Ni-Ti-Mn alloy. The cast structure revealed Ti-rich precipitates(X_L phase) between dendrite arms, which have been identified as (Cu,Ni)₂TiAl intermetallic compounds. By homogenizing above 900℃, the X_L phase was melted in the matrix, while the X_s phase was precipitated in matrix and the volume fraction of it was increased. When hot-rolled specimen was betatized below 750℃, recrystallization could not be observed. However, the specimen betatized above 800℃ was recrystallized and the grain size was about 50㎛, while X_s phase was precipitated in matrix. With raising betatizing temperature, M_s and A_s temperatures were fallen and transformation hysteresis became larger. The strain of the specimen betatized at 800℃ was 8.2% as maximum value. The maximum shape recovery rate could be obtained in the specimen betatized at 800℃ but it was decreased due to the presence of X_s phase with increasing betatizing temperature.
Fe-15Mn-5Cr-5Co-3Si 합금에서ε 마르텐사이트의 방향성
신명철,지광구,장우양,양권승 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.4
The microstructural difference between thermal and stress-induced ε martensite was investigated in iron-based shape memory alloy. The thermal εmartensite plates were found to be randomly distributed with several variants, causing no shape change during cooling and heating. But stress-induced ε plates have almost single variant in one grain. Pole figure analysis showed that ε plates whose [1.63 0 1] ε direction is paralell to tensile stress are preferably formed on the deformation. The [1.63 0 1] εdirection was proved to be the most expandable one in fcc→hcp transformation by [112] γ shear deformation.