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Fe-25at% Al 금속간화합물의 입계부식거동에 미치는 Cr, Mo, Nb 및 B의 영향
최답천,최한철 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.4
Effects of the addition of Cr, Mo, Nb, and B to Fe-25at%Al intermetallic compound on the intergranular corrosion behavior were investigated using potentiostat. The specimens were casted by the vacuum arc melting. The subsequent homogenization and the stabilization led to the homogeneous DO₃ structure of the specimen. After the corrosion tests, the surface of the tested specimens were observed by the optical microscopy and scanning electron microscopy(SEM). For Fe-25at%Al intemetallic compound, the addition of Cr and Mo proved beneficial to decrease the grain boundary attack by decreasing activation current density. Addition of B and Nb resulted in a higher activation current density and also a higher passive current density. These results indicated the role of Cr and Mo in improving the intergranular corrosion resistance of Fe-25at%Al intermetallic compound. Boron and Nb addition to Fe-25at%Al accelerated the granular and also the intergranular corrosion. Fe-25at%Al containing Cr and Mo showed remarkably improved intergranular corrosion resistance in comparison with Born and Nb addition to Fe-25at%Al.
Fe-Cr-Al 3 원계 합금의 미세조직, 기계적 성질 및 파괴거동에 미치는 첨가원소의 영향
최답천,이도재,이광민,주성민,최한철 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.2
Fe-Cr-Al alloy has been used in automobiles to meet the social needs for clean exhaust gases and reduced weight for better fuel economy. Various other types of high performance Fe-Cr-Al alloy are now being used in the automobile exhaust system. This paper described the changes in the microstructures, mechanical properties and fracture behaviors for automobile exhaust system parts application. As the amount of 0.05 wt.%B or 0.5 wt.%Zr addition was added, the grain size became smaller. The results of XRD were observed α-ferrite(α-Fe) for Fe-(5∼20)wt.%Cr-(5, 6, 8)wt.%Al alloys. However, Fe-(5∼20)wt.%Cr-10 wt.% Al alloys were observed α-ferrite(α-Fe) and α₁(Fe₃Al). Rockwell hardness was increased by increasing Cr and Al amount. Yield strength was decreased by adding 0.5wt.%Zr. Regardless of Cr amount, fracture behaviors in 5 wt.%Al added alloys revealed quasi-cleavage and ductile fracture mode, and 10 wt.%Al added alloys revealed brittle fracture mode with cleavage and river pattern. However the fracture mode in 0.05 wt.%B and 0.5 wt.%Zr added alloy revealed quasi-cleavage and dimple fracture mode due to strengthening of grain boundaries, respectively.
Cr 과 Si 이 복합 첨가된 TiAl 금속간화합물의 미세조직 및 기계적 성질에 관한 연구
최답천,이호종,이병택 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.8
In order to investigate the effects of Cr and Si additions in γ-TiAl alloy, the microstructure and mechanical properties before and after heat treatment were studied. Simultaneous additions of Cr and Si were more effective in stabilizing the lamellar structure of TiAl alloys after heat treatment. The stoichiometric composition of the precipitates formed in the alloy with 0.5% Si addition was estimated to be Ti_5(Si, Al)₃, and that with 3%Cr0.5%Si addition to be(Ti, Cr)_5(Si,Al)₃. Good mechanical properties could be achieved by simultaneous addition of Cr and Si. Tensile tests before and after heat treatment showed that maximum yield strength was obtained from the alloy with 1%Cr0.5%Si addition and while the highest elongation was observed by 1%Cr0.25%Si addition before heat treatment. However, the alloy with 2%Cr0.5%Si addition showed the highest elongation after heat treatment.
고강도 내마모 금속간화합물 / Al 기지 복합재료의 개발을 위한 기초연구
최답천,이경구,이호종,기회봉 ( Dap Chun Choi,Kyung Ku Lee,Ho Jong Lee,Whe Bong Ghi ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.3
N/A The interfacial phenomena between intermetallic compounds and Al matrix have been studied at 680℃ for various holding time under argon atmosphere. Model experiments were performed using Fe, Ni and Ti wire to observe the interfacial phenomena. The interfacial phenomena between intermetallic compounds and Al matrix were analysed by optical microscope, SEM and EDX. The results of EDX and XRD showed that the interfacial zones of intermetallic compounds/Al matrix were composed of several intermetallic layers. The reaction layer was varied with holding time and heating temperature. The investigation of interfacial zones in the specimen as a function of heat treatment time at 680℃ indicated that the best heat treatment condition for squeeze casting was 680℃ for 5min.
주철의 기지조직에 (基地組織) 미치는 Mischmetal Hydride 의 첨가효과
최답천,진영철 ( Dap Chun Choi,Young Chul Jin ) 한국주조공학회 1988 한국주조공학회지 Vol.8 No.4
N/A In this study we have investigated the effects of Mm, MmH and MmH₂ on the matrix development in cast iron, The conclusive summary is as follows : The spheroidal graphite was observed when 0.5wt.% or more of mischmetal was added and the matrix was of ledeburite structure, but hull`s eye structure was not observed. On the other hand, the bulls eye structure was observed when 0.25wt.% of MmH, or 0.25wt.% to 0.5wt.% of MmH₂was added. Above limit of the additives, the matrix changed into ledeburite structure. As the hydrogen content of mischmetal compound increased from MmH, the range of additives to obtain bulls eye structure expanded. This reveals the significant effect of mischmetal hydride on matrix development in cast iron and the possibility of practical use of the additives.
용탕단조법에 의한 금속간화합물 / Al 기지 복합재료 개발을 위한 기초연구
최답천,이경구,이연오 ( Dap Chun Choi,Kyung Ku Lee,Yeon O Lee ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.5
N/A The microvickers hardness and microstructure of Fe/Al composite fabricated by squeeze casting method were investigated. Pure Al and A356 Alloy were chosen for the matrix composition and Fe preform was fabricated with sintered Fe powder at 1000℃ for 30min. under hydrogen atmosphere. Experimental variables were included preheating temperature, melt temperature and applied pressure. Analysing the experimental result concerning microstructure of fabricated composites, Fe/A356 composite showed improved microstructure at 600℃ melt temperature and 350℃ preform preheating temperature in Fe distribution and Infiltrated distance. The results of EDX and XRD showed that the interfacial zones of Fe/Al composite were composed of non-equilibrium intermetallic layers[(Al_5Fe₂)_x, Al_(13)Fe₄m Fe₃Al, FeAl]. The microvickers hardness of Fe/Al composite showed higher value than Fe/A356 composite in interface.
최답천,황금연,강창석,명태호,Mishima, Yoshinao 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.11
A new class of Co-base superalloy may be developed based on the ternary Co-Al-C system in which two phase alloys could be designed containing E2₁-type intermetallic compound Co₃AlC_x, known as κ-phase, being dispersed in the Co primary solid solution. Strength and ductility of the two phase alloys are evaluated at room to elevated temperatures. It is found that compressive 0.2% flow stress of the two phase alloys at room temperature seems to exhibit a maximum with 30 to 50% volume fraction of the intermetallic phase. Room temperature ductility of the two phase alloys is found to be 5 to 21% varying monotonously with increasing volume fraction of the intermetallic phase. At 1000℃, the 0.2% flow stress of the two phase alloys with κ-phase for more than 30% in volume are about 250 to 280 ㎫ under a strain rate of 1.4 ×10^(-4)s^(-1), which is comparable to that of commercial nickel base superalloy.