발표30 : Al-Li 합금의 δ'-PFZ 의 성장에 미치는 Sc 첨가의 영향

조충형,(Y . Miura) 대한금속재료학회 ( 구 대한금속학회 ) 1999 대한금속학회 추계학술대회 개요집 Vol.1999 No.-

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.

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.

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.

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.

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.

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.

Zr-2.5Nb 압력관의 파괴인성 특성

부명환(Myung-Hwan BOO),조충형,김상재(Sang-Jai KIM),임경수,김영석(Young-Suk KIM),Dong-Jun OH,Sung-Soo KIM 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.3

The aim of this study is to investigate fracture toughness of a Zr-2.5Nb pressure tube with temperature. The tensile and fracture toughness tests were performed at temperatures ranging from room temperature to 300℃ on tensile and curved compact tension, CCT specimens. The CCT specimens were directly cut from the tube retaining original curvature using wire cutting machine. The Zr-2.5Nb tube had a decrease in yield and tensile strengths with increasing temperature. However, its elongation had a maximum at 150℃ followed by a decrease with increasing temperatures. The loss of ductility which was stricking in the temperature range of 200~250℃ determined the fracture toughness resistance, dJ/da of the Zr-2.5Nb tube with temperature, resulting in the maximum in the range of 100~150℃. The temperature dependence of the fracture toughness for the Zr-2.5Nb tube is discussed fracture in association with the formation of secondary crack on the fractured surfaces.

폐타이어를 이용한 제강분진 처리를 위한 기초연구

황용길,이상화,이성룡,정석수,최재신,조충형 한국자원리싸이클링학회 1995 資源 리싸이클링 Vol.4 No.4

분진 중에 함유된 Zn, Pb, Fe 등의 유가 금속을 회수하기 위해 폐타이어를 건류하여 만든 건류탄소를 환원제로 이용하여 재활용하고자 하였으며 또한 분진을 Pelletizing 하거나 Briquetting해서 환원 처리할 때, 공해 발생과 작업상의 단점을 보완하기 위하여 제지공장에서 발생하는 폐펄프와 분진 및 건류탄소를 소정의 비율로 혼합한 후 성형한 다음 통기도 및 압축강도실험 등을 한 결과 다음과 같은 결론을 얻었다. 동일한 건류탄소 첨가량에서 결합제로 사용한 폐펄프의 첨가량이 증가할수록 통기도는 증가하며 이는 시편내 Porosiaty에 기인한 영향이라 생각되며, 동일 첨가량의 폐펄프에서 건류탄소의 첨가량이 증가할수록 통기도는 증가하는 경향을 보이며 압축강도는 건류탄소의 비율과 소결온도에 따라 증가 감소의 현상이 다소 상반되는 결과가 나타났다. 건류탄소 20%, 폐펄프 10%를 첨가하여 만든 Briguetting 시료를 X-선 회절분석 결과 $800^{\circ}C$에서는 ZnO와 $Fe_3$$O_4$가 조사되었으나 $1000^{\circ}C$ 이상에서는 ZnO와 $Fe_3$$O_4$를 확인할 수 없었다. $1000^{\circ}C$에서 소결실험을 한 결과 아연, 철산화물이 분해 증발하여 아연품위가 62%인 조산화아연물을 얻을 수 있었다. Distillation oI the dust generated during waste tue pyrolysis was perIomerl to rccover valuable metal sucll as zlnc. lead and iron. Pemcahilily and carnprcssivc tests were pursucd to ahlain the basic dala for cslraclian of zinc from the slntering propcrtp ol stccl making dusts and distilled carhon of waste tires as wcll as wastc pulp sludge mixlure hr~quet were investigated at various sinlcring lempcraturcs. Permeablllly rncieased with increastng amount of waste pulp in specil~cd istilled carhon due tn the fnrmat~ono f porusily in lhe sample TIE co~npress~vsctr ength showed the vanous values wlth different amDunl of dislilled-carhon adrlit~nilsa nd at diIIerenl sinlering tcmpcralures. X-ray diffifraction anvlyscs oI a hnquet rn~rhtre of steelmaking dusts(20Q didilled carhon and 10% waste pulp sblered ;>I SOOT) showcd thal the briquet consisted ot ZnO and Fc,O.,, hut was not found at the hriguet rintered at over 10OO'C. Crude zinc oxide sintered a1 IOOOC contained OZA Zn.

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.