GTA 용접처리한 Zircaloy-4판재의 미세조직 및 기계적 성질

조충형(Chung-Hyung Joh),김상재(Sang-Jai Kim),김선식(Seon-Sik Kim),임경수(Kyung-Soo Im),김영석(Young-Suk Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8

To predict degradation of the reflector vessel made of annealed zircaloy-4 alloys their microstructures and tensile properties were investigated because irradiation growth strongly depends on metallurgical variables as composition, dislocation density, texture, grain size and residual stress. The plate has fully recrystallized grains, low dislocation density, two kinds of second phase particles as Zr(Fe,Cr)₂ and Zr₃Fe or Zr(Fe, Cr)₂, and a texture where most of basal poles are oriented toward the direction normal to thickness. Further study is necessary to evaluate basal pole intensity, f<SUB>L</SUB> with high confidence because its small change strongly affects the irradiation growth. The plate shows that higher YS, similar strength and larger elongation in the RD, compared to those in the direction normal to the RD. Welded region shows somewhat lager strength and YS at RT and smaller elongation than matrix. The welded region is concluded to have low residual stress as a results of post-weld anneal and similar hardness as that of matrix.

X-선 회절에 의한 피로파면거동과 응력세기계수 예측에 관한 연구

임만배(Man-Bae Lim),부명환(Myung-Hawn Boo),조충형(Chung-Hyung Joh),김영석(Young-Suk Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3

This study investigated the effect of stress intensity factor ranges, or ΔK=Kmax-Kmin on residual stress for SG365 steel. The fatigue crack growth rates of the SG365 steels were determined at RT and 300℃ on the compact tension specimen under the ratio of Pmax and Pmin set at 0.1 and 0.5, respectively. To correlate ΔK and residual stress and the FWHM are measured on the fractured surface of the CT specimens using diffraction lines {211} determined by an X-ray residual stress tester. The Residual stress had no clear trend with ΔK but the FWHM had a nice linear relationship with ΔK. Based on the these results, the predictability of ΔK is discussed as a function of the FWHM and residual stress, if any, determined by X-ray diffraction lines.

A1-Sc 희박합금에 있어서 전기저항측정에 의한 Sc 원자와 공공간의 결합에너지

조충형,미포강굉 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.10

The binding energy for a Sc atom-vacancy couple was determined in an Al-0.0087 at%Sc alloy by the resistivity measurements. For pure Al, the formation energy of a vacancy was determined to be 0.79 eV, being in good agreement with those in the literature. The apparent vacancy formation energy in a dilute Al-0.0087 at%Sc alloy was 0.65 eV. Clearly it is somewhat lower than that for a pure Al which suggests the presence of a vacancy as a vacancy-solute couple in the Al-Sc alloy. On the basis of semi-emprical calculation using the vacancy formation energies in pure Al and in the dilute Al-Sc alloy and using the relationship proposed by Lomer(IOM series, no.23(1958)p.85), the vacancy-Sc binding energy for Sc was found to be 0.35 eV. The value, 0.35 eV, obtained in this study is larger than those observed for other transition elements in Al. This high vacancy-Sc binding energy is considered to affect the precipitation behaviors in Al-Sc alloys.

A1-Li 합금의 Sc 첨가에 따른 δ'-Al3L 입자의 조대화 특성연구

조충형,미포강굉 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.3

Effects of Sc on the coarsening process of δ'-Al₃Li precipitate in Al-Li allays, which have been regarded as a main hardener, were investigated by means of DSC, TEM and hardness tester. From the result of DSC analysis, both exothermic and endothermic peaks of the Sc-containing alloy, which correspond to the precipitation and dissolution of δ' particles, were observed to shift to the higher temperature sides, compared to those of the Sc free alloys. This suggests that Sc solutes could act as a prohibiter of precipitation and growth of the δ' particles. The estimated activation energy for δ' precipitation and growth in the Sc-containing alloy is 60 kJ/㏖ larger than Sc-free alloy 47 kJ/㏖. From the result of microstructure observation by means of TEM, both alloys revealed that the growth of mean diameter of δ' particles is proportional to the cube root of time and, especially in the Sc containing alloy, a much decreased coarsening rate of the δ' particles is observed. According to the result of EDX analysis, no peak of Sc solute was detected in the δ' particle of the Sc containing Al-Li alloy, which indicates that there is no Sc enrichment in the δ' particle. Therefore, based on the present experimental results, the reason for the retardation of δ' precipitate by the Sc addition is closely related to the strong interaction between Sc solutes and vacancies in the matrix.

Al-Li-Sc 합금에 있어서 δ'-PFZ 의 성장특성

조충형,미포강굉 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.7

δ'-PFZ growth behaviors in Al-Li alloys at various aging conditions were investigated mainly by TEM observations. The widths of PFZs were increased with aging time and aging temperature and their growth is proportional to the square root of aging time. The alloy containing Sc showed a smaller value of growth rate constant and larger activation energy for the PFZ growth than those of other Sc-free alloys. These facts indicate that diffusion process of Li solutes via vacancies could be precluded or limited by Sc in solution. In the Sc containing alloy, high density of dislocations surrounded by coarsened Al₃Sc particles were observed in the overaged condition. These dislocations can be closely linked to the reduction of growth rate of the PFZ, considering that they provide sink sites for lattice vacancies, finally leading to suppress the diffusion of Li solutes toward grain boundaries.

폐전선 피복재 건류탄을 이용한 제강분진처리를 위한 기초연구

황용길,이상화,이성룡,정석수,최재신,조충형 東亞大學校 1995 東亞論叢 Vol.32 No.-

Distilled carbon from waste electric wire coated by vinyl is used to recover valuable metal such zinc, lead and iron in dust. Pemeability and compressive tests are who done to present basic data on extraction of zinc in dust. Experimental results obtained from sintering property of steelmaking dust, distilled carbon from waste electric wire coated by vinyl and waste pulp sludge mixture briquet at various sintering temperature are as followings; Permeability is increased as increasing distilled carbon and pulp amount at higher temperature than room temperature condition. Compressive strength at room temperature is increased as increasing distilled carbon and decreasing waste pulp amount, but decreased as increasing temperature and waste pulp amount. Weight Loss reaction experiment is increased a increasing distilled carbon and waste pulp amount. ZnO and Fe₃O₄ are obtained from sample containing ZnO, Fe₂O₃ and ZnO at 800℃. Permeability test at 500℃ and 800℃ did not well, because of 13.3% CaO in distilled carbon. Sample because semmi melted state at 1000℃. Distilled carbon obtained from waste electric wire showed effect of reduction and flux material.

황산스트론튬으로부터 탄산스트론튬으로서의 전환에 관한 연구

이성룡,조충형,황용길 東亞大學校 大學院 1995 大學院論文集 Vol.20 No.-

This study to convert strontium sulfate into strontium carbonate after reduction to strontium sulfide soluble in water was performed with sodium carbonate solution at various temperature. The results obtained from the above are as follows. The reduction temperature of strontium sulfate to strontium sulfide was 800℃. But strontium sulfide was reoxidized to strontium sulfate at the over 1000℃. Lid of reaction vessel closed up influenced increasing carbon activity during the reduction of strontium sulfate to strontium. Leachability of strontium sulfide reduction from strontium sulface in water was increased at high temperature, but decreased at 6mole carbon ratio because of excess carbon not reacted. Recovery of strontium carbonate from strontium sulfate was high at he high concentration of sodium carbonate solution, but low at 3 and 6 mole carbon ratio relatively Recovery of strontium carbonate from strontium sulfide was increased at high temperature, but decreased at 3 and 6 mole carbon ratio relatively. Agitation effect so accelerated to increase recovery of strontium carbonate. Impurities exist in cellestite as calcium sulfate, calcium carbonate, barium sulfate and barium carbonate compounds were not converted into other compounds during reduction of strontium sulfide from strontium sulfate. These compounds insoluble in water are able to be removed during water leaching of strontium sulfide.