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장우양,양권승,강조원 조선대학교 생산기술연구소 2003 生産技術硏究 Vol.25 No.2
In order to clarify the effect of the composition and wheel speed on the phase stability of parent phase, the Cu-AI-Ni based alloy ribbons with different Al content were manufactured by rapid solidification process at various wheel speed. The effect of heat treatment on the microstructure and transformation characteristics of the ribbons with fiber structure have been studied by using OM, SEM, TEM, XRD and DSC. The parent phase was retained in the ribbon fabricated at a faster wheel speed even the same composition or in the ribbon contained higher Al content even at the same wheel speed. As flash-heating temperature increased from 750℃ to 850℃, the retained parent phase disappeared and peak of martensite phase only appeared. When ribbon A5 was aged at 60℃ for 10, 24, 48 and 72 hour, no remarkable changes was observed with increasing in aging time. Transformation temperatures in ribbon AS aged at 60℃ for 10, 24, 48 and 72 hour were lower than those in ribbon A5 in as-spun ribbon. When the ribbon A5 was aged at 100℃ for 10, 24, 48 and 72 hour, both retained parent phase and martensite were observed in the ribbon A5 aged for 10 and 24 hour observed. Microstructure of cross-sectional surface of ribbon aged at 100℃ for 72 hour was changed to columnar structure and transformation temperature rose only ribbon A5 aged for 72 hour.
Austenitic Stainless Steel의 應力腐蝕龜裂에 關하여 : 沸騰 MgCl₂溶液의 濃度變化를 中心으로
張禹煬 조선대학교 생산기술연구소 1981 生産技術硏究 Vol.1981 No.-
Stress corrosion cracking (SCC) of austenitic stainless steels has been investigated for several concentrations of boiling MgCl₂solutions. The cracking mode of austenitic stainless steels was investigated for several concentrations of boiling MgCl₂solutions by microscopy. The tests were conducted on stressed U-bend specimens cut from sheets. Both the periods of induction and propagation were determined by measuring the crack depth of the specimens for several concentrations of boiling MgCl₂solutions, and the mechanism was discuesed. The results obtained are as follows: 1) SCC occurs at the region of stress concentration, and it is always perpendicular to the direction of tensile stress. 2) As the concentration of boiling MgCl₂solution increases, SCC is mainly transgranular. Conversely, as the concentration of boiling MgCl₂solution decreases, SCC is intergranular. 3) As the concentration of boiling MgCl₂solution increases, the induction period increases and the propagation period decreases. Therefore, as the induction period increases, the propagation period decreases. 4) Time to failure shows a minimum at 140-150℃, and it increases below and/or above 140-150℃.
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 계 형상기억리본 제조시 냉각속도에 따른 미세조직 및 변태특성
장우양,이영수,이은구 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.4
The microstructural change and transformation characteristics with cooling rate i.e. wheel speed were investigated in 82.8wt%Cu-12.8wt%Al-4.3wt%Ni SMA ribbons fabricated by melt-spinning. The thickness and width of ribbon were decreased with increasing wheel speed, while the uniformity of it was improved. At same wheel speed, the grain size of the contact surface of ribbon was smaller than that of free surface. The mean grain size was decreased with increasing wheel speed, resulted in obtaining grains with 3㎛ in mean diameter in the wheel speed of 30m/s. However, micro-voids and cracks at grain boundary could be observed at higher wheel speed. M_s, and A_s temperatures were decreased, and M_s∼M_f and A_s∼A_f temperature ranges were broadened with increasing wheel speed. All the ribbons were retained the ordered DO₃due to rapid cooling, the volume fraction of it was increased with increasing wheel speed.
Cu-Al-Ni계 합금 선재의 의탄성 거동에 미치는 미세조직의 영향
장우양,김경훈,은상원,강조원 조선대학교 생산기술연구소 2005 生産技術硏究 Vol.27 No.spec
In order to realize the psuedoelastic behavior of polycrystalline Cu-Al-Ni based alloy, Cu-Al-Ni based alloy rod with unidirectional solidification structure was fabricated by heated-mold continuous casting process. When the cast rod was betatized at the elevated temperature above 700℃, the Y₂ phase is gradually dissolved into the matrix so that the volume fraction of the Y₂ phase was decreased. The compressed specimen was completely recovered upon unloading, resulting in pseudoelastic behavior. The pseudoelastic strain of 10 % could be obtained in cast rod betatized above 700 ℃. However, the stress-strain curves for compression test were not same with 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 not linear.