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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.
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℃.
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.
Cu-Al-Ni계 초탄성 합금의 변태특성 및 변형거동에 미치는 미세조직의 영향
박정수,김경훈,은상원,조무현,장우양,양권승,강조원 조선대학교 생산기술연구소 2004 生産技術硏究 Vol.26 No.2
The effect of microstructure on transformation characteristics and deformation behavior in Cu-Al-Ni based superelastic alloy has been studied in alloy by using metallography, calorimetry, compression test and XRD. When the alloy betatized at the elevated temperature above 600℃, the r₂ phase completely dissolved into the matrix. The β₁' or r₁' martensites from β₁ patent phase was transformed in as-cast state but the parent phase stabilized by betatizing at 600℃. With increasing betatizing temperatures above 600℃. both₁' and r₁' martensites again transformed from β₁ parent phase and the heat flow of r₁' martensite was higher than that of β₁' martensite for reverse transformation. The compressed specimen, showing pseudoelastic behavior, was completely recovered upon unloading. However, the stress-strain curves for compression test were different by betatizing temperature; the stress-strain curves of the specimen betatized at 600℃ and 700℃ were linear but those of the specimen betatized at 800℃ and 900℃ were non-linear. The r₁' martensite was retained after compression test and the volume fraction of that increased with increasing betatizing temperature and strain.
급속 응고된 Fe-24%Mn-4%Si-5%Cr-5%Co 합금 리본의 열처리 및 인장변형 특성
김경훈,M. Kiabilan,강후원,양권승,한재익,장우양,강조원 조선대학교 생산기술연구소 2005 生産技術硏究 Vol.27 No.2
Effects of heat treatment and tensile deformation characteristics on the microstructure and martensitic transformation chracteristics have been studied in rapidly solidified Fe-24Mn-4Si-5Cr-5Co based alloy ribbon by using metallography, calorimetry, X-ray diffractometry and tensile test. The volume fraction of ε martensite as well α' martensite is increased due to thermal stress relief and grain growth with increasing annealing temperature. Yield stress of melt-spun ribbon is decreased with increasing wheel speed; yield stress is 40.6kgf/㎟ in the ribbon fabricated at a wheel speed of 50m/sec. It can be concluded that the dependence of yield stress is contributed to the microstructure of melt-spun ribbon.
CuAlNi 형상기억합금의 결정립 크기 및 제 특성에 미치는 가공열처리의 영향
이영수,강후원,김윤채,장우양,강조원 조선대학교 생산기술연구소 1996 生産技術硏究 Vol.18 No.1
The effect of thermomechanical treatment such as hot-rolling and subsequent annealing conditions has been studied. and the variations of mechanical properties. transformation temperature and shape memory ability with annealing time have been investigated in CuAlNi shape memory alloys by metallography. calormetry and X-ray diffraction. The grain of the specimen hot-rolled below 800℃ was deformed and elongated but the grain of the specimen hot-rolled above 800℃ was partially recrystallized. The grain size after hot-rolling decreased with decreasing hot-rolling temperature and with increasing the rate of reduction in thickness. By the chage of cooling rate after hot-rolling, the microstructure of the hot-rolled specimen could be controlled and it has affected grain size during recrystallization. The grain size could be markedly decreased by intermediate annealing between hot rolling process; the smallest grain with the size of 95㎛ could be obtained by recrystallization at 700℃ for 7min after the combination of intermediate annealing and hot-rolling process. With increasing recrystallization time. M_(s) and A_(s) temperatures increased but transformation hysteresis decreased. The difference in the fracture surface could be clearly observed with recrystallization time. With increasing annealing time in order of 3min, 5min and 7min at 700℃. the fracture mode has changed to the mixture of intergranular and transgranular fracture with the latter being dominant, to transgranular fracture and to intergranular fracture, respectively. In the case of annealing at 700℃ for 5min. shape memory ability could be obtained maxium value by 74% but it was sligtly decreased to 60% with increasing time.