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진영철,국진선,김양수,홍은성,이민상,이민호,유창영 ( Y . C . Jin,J . S . Kook,Y . S . Kim,E . S . Lee,M . H . Lee,C . Y . Yoo ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.1
The effects of alloying elements on the superplastic properties of Al-Li based alloys had been investigated. The intermediate thermo-mechanical treated(ITMT) Al-2.0wt%Li, Al-2.0wt%Li-1.0wt%Mg, Al-2.0wt%Li-0.12wt%Zr and Al-2.0wt%Li-1.2wt%Cu-1.0wt%Mg-0.12wt%Zr alloys were tested in tension at various temperature (400, 450, 500 and 550℃) and strain rate(6.7×10^(-3), 1.0×10^(-2), 1.6×10^(-2) and 5.0×10^(-2)/sec). The results were as follows : The superplasticity in binary, ternary and pentanary alloys appeared at 500 to 550℃, and good strain rate for superplasticity, 1.6×10^(-2)/sec∼1.0×10^(-2)/sec for a binary alloy and 1.0×10(-2)/sec∼6.7×10^(-3)/sec for ternary and pentanary alloys. A Zr-added ternary alloy had best value of elongation (730%) in four alloys at 550℃ of tension temperature and 1.0×10^(-2)/sec of strain rate. The strain rate was greatly dependent on tension temperature and true strain rate was more than 1.0 at all test temperature and strain rate. In binary and Mg-added teranry alloys, the necks were slightly formed and their fracture surface had lips shape, but Zr-added ternary and pentanary alloy fractured along the grain boundary without necking. Their dislocations moved to grain boundary during superplasticity deformation and arranged perpendicular to grain boundary. Superplastic deformation was made by grain boundary slip of dislocation slip creep and model of core and mantle.
진영철,홍은성,김양수,이민상,유창영 ( Y . C . Jin,E . S . Hong,Y . S . Kim,M . S . Lee,C . Y . Yoo ) 한국열처리공학회 1993 熱處理工學會誌 Vol.6 No.1
To investigate the properties of diffusion bonding of 7050 Al alloy, the diffusion bonding joints have been produced in self-made diffusion bonding hot-press which admits a defined application of the bonding pressure during the heating phase and also rapid cooling after the bonding process with various bonding condition. The strength of the bond increases with increasing the bonding time and temperature. Shear test at toom temperature showed that high strength up to 70% that of parent metal (320㎫), 220㎫ for the specimen bonded 14hr at 560℃, with 3㎫. In this case, however, there is large deformation more than 20% reduction in thickness. The results were correlated with joint characteristics found by optical microstructure and by fractography by SEM. When the strengths of the bonds are more than 50% that of parent metal, a great deal of dimples stretched along the direction of shear stress are observed over the fractured surface of the bond. On the microstructure of the bond line, initial mophology of the bond line disapeared for the grain boundary migration with increasing tire bonding time.
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.
유창영,진영철 ( C . Y . Yoo,Y . C . Jin ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.3
In this study, intermediate thermo-mechanical treated Al-2.0wt%Li, and Al-2.0wt%Li-1.2wt%Cu-1.0wt%Mg-0.12wt%Zr alloys were tested in tension at 10℃ and elevated temperature (100, 200 and 300℃). The results are follows : The tensile strength of Al-Li-Cu-Mg-Zr alloy is the highest but the elongation of Al-Li alloy is the highest(106%) among the all alloys in tension at 300℃. The Portervin-LeChartlier effect is showed in Al-Li-Cu-Mg-Zr alloy at 10 and 100℃, because of tangled dislocation by Mg and Cu. In the true stress-strain curves of all alloy, the peaks of stress at 300℃ are showed at the strain less than 0.1. In the binary alloy, the dynamic restoration process at 200 and 300℃ is nearly similar to dynamic recovery type. The hot deformation stress is decreased with increase of dynamic recovery degree, but the elongation is increased. When the strain the strain rate are constant, the temperature dependence of hot deformation stress is increased with increase of deformation temperature. The elongation and degree of dynamic recovery are decreased with increase of hot deformation activation energy, but the deformation stresses slightly increased.
김성종,장경환,진영철,정경락 ( S . J . Kim,G . H . Chang,Y . C . Jin,G . R . Jheong ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.1
Anatase TiO₂particles prepared by experiment were used to study the change of crystal structure by calcination temperature. The results were as follows. Crystallite size of anatase TiO₂particles increased with calcination temperature. The rate of increasing the crystallite size of anatase TiO₂particles was decreased below 700℃ and was markedly increased above 700℃. Unit cell volume of TiO₂was expanded at low temperature and was contracted at high temperature. This result means that the growth of crystallite size was occured in the direction.
국진선,전우용,진영철,김상협,Guk, Jin-Seon,Jeon, U-Yong,Jin, Yeong-Cheol,Kim, Sang-Hyeop 한국재료학회 1997 한국재료학회지 Vol.7 No.3
과냉각액체구역(${\Delta}T_{x}=T_{x}-T_{g}$)을 갖는 $Fe_{80}P_{10}C_{6}B_{4}$ 조성에 천이금속(Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Ni, Pd, Pt및 Cu)를 첨가하여 이들 원소가 유리화온도($T_{g}$), 결정화온도($T_{x}$) 및 과냉액체구역 (${\Delta}T_{x}$)에 미치는 영향에 \ulcorner여 조사하였다. $Fe_{80}P_{10}C_{6}B_{4}$ 합금의 ${\Delta}T_{x}$ 값은 27K였으나 이 합금에 Hf, Ta 및 Mo을 각각 4at%첨가하면 그 값이 40k 이상으로 증가하였다. 이같은 ${\Delta}T_{x}$ 값의 증가는 유리화온도($T_{g}$의 상승보다 결정화온도($T_{x}$)의 상승폭이 크기 때문이다. $T_{g}$ 및 $T_{x}$는 외각전자밀도(e/a)가 약 7.38에서 7.05로 감소할수록 상승하였다. e/a의 감소는 천이금속과 다른 구성원소(반금속)사이의 상호결합상태를 의미한다. 즉 $T_{g}$ 및 $T_{x}$의 상승은 강한 상호결합력에 기인하는 것으로 사료된다. At the aim of finding a Fehased amorphous alloy with a wide supercooled liquid region (${\Delta}T_{x}=T_{x}-T_{g}$) before crystallization, the changes in glass transition temperatudfI$T_{g}$ and crystallization temperature ($T_{x}$) by the dissolution of additional M elements were examined for the $Fe_{80}P_{10}C_{6}B_{4}$(x~6at%. M= transition metals) amorphous alloys. The ${\Delta}T_{x}$ value is 27K for the Fe,,,P,,,C,,R, alloy and increases to 40K for the addition of M=4at%Hf, 4at%Ta or 4at%Mo. The increase in ${\Delta}T_{x}$ is due to the increase of $T_{x}$ exceeding the degree in the increase in $T_{g}$. The $T_{g}$ and $T_{x}$ increase with decreasing electron concentration (e/a) from about 7 38 to 7.05. The decrease of e/a also implies the increase in the attractive bonding state between the M elements and other constitutent elements. It is therefore said that $T_{g}$ and $T_{x}$ increase kith increasing attractive bonding force.