非鐵金屬의 Boron化에 의한 表面硬化

徐昌濟,文貞勳,林秉守 成均館大學校 科學技術硏究所 1992 論文集 Vol.43 No.2

Boriding has been investigated by means of a furnace heat treatment burying in amorphous boron powder under an argon atmosphere. the hardness of the boronized surface on the Cu-Ni alloys showed the range of Hv 500 to 10000 depending on chemical compositions. The boronized surface of the alloys has been investigated from metallographic and X-ray analysis and hardness distribution. Finally hardness estimation of boronized surface of Cu-Ni alloys has been tried using the experimental results of hardenability of Cu-Ni alloys.

海水中 알루미늄合金의 陽極分極特性에 미치는 合金元素의 影響

徐昌濟 成均館大學校 大學院 1976 首善論集 Vol.1 No.1

Al-Mg 合金의 水素脆性에 관한 硏究

徐昌濟 成均館大學校 科學技術硏究所 1983 論文集 Vol.34 No.2

The effect of activated hydrogen has to bo studied in hydrogen embrittlement by an atmosphere or chemical reaction. According to this study, when hydrogen charged compulsively by cathodically electrolytic process, its change of content, the state of existence and the behavior of embrittlement were investigated in A1-8% Mg alloy. The results are as follows: 1. Hydrogen content increases with charging time and increases adraptly up to 10 minutes and saturates at about 30 minutes 2. Permeated site of hydrogen are octahedral site, but in tetrahedral site, it is permeated with slight strain. 3. Tensile strength and elongation are decreased with hydrogen charging time by diffusion of hydrogen, but elastic property is unchanged. 4. Permeation of hydrogen results in intergranular brittle fracture mode, the degree of embrittlement is proportional to the content of permeated hydrogen. In A1-8% Mg alloy, it is considered that permeated hydrogen affected to result in intergranular brittle fracture by Prefferred permeation into grain boundaries and precipitates.

低密度 高强性 Al-Li系合金의 接合性에 關한 硏究

徐昌濟,金鍾賢,金亨泰,李彰培 成均館大學校 科學技術硏究所 1995 論文集 Vol.46 No.1

This paper is study on the weldability of Al 8090 alloy which is Li-containing aluminium alloy. This alloy has increased elastic modulus and reduced density compared with conventional aluminium alloys. The weldability of Al 8090 alloy was studied using GTAW(gas Tungsten Arc Welding) with A 40443 and A 5356 filler metal. The quality of the weld was evaluated through mechanical test and microscopical observation, and crack susceptibility was evaluated through varestraint test. In the varestraint test, a bending strain was imposed during welding on the specimen. The total crack length(TCL) and maximum crack length(MCL) were taken as measured of the crack susceptility. After the weldability of Al 8090 alloy was analyzed compared with Al 2024 alloy and Al 7075 alloy, the results were obtained as follows. 1. The hardness distribution of Al 8090 alloy showed up a equal level in comparison with hardness distribution of Al 2024 alloy, Al 7075 alloy. 2. Crack susceptibility with Al 8090 alloy was lower than that with Al 2024 alloy and Al 7075 alloy. 3. The Li added in Al 8090 alloy assists in improving the resistance to crack propagation. 4. The mechanism of fine-grain region formation probably lies in the heterogeneous nucleation aided by Zr. 5. MCL was liner to TCL in Al 8090 alloy, Al 2024 alloy, Al 7075 alloy.

Al合金系에 있어서 微細偏析에 미치는 凝固樣式의 影響

徐昌濟 成均館大學校 1983 論文集 Vol.33 No.-

In the dendrite structures of unidirectionally and freely solidified Al-Cu and Al-Mg alloys, the effect of cooling rate on microsegregation and the solution kinetics of nonequilibrium second phase were studied by means of X-ray diffraction and method of point count. The main conclusions obtained are as follows; 1) It was found that lattice parameter (a) of alloys change with only the cooling rate without the solidification modes and the kind of alloys. 2) As the cooling rate increases, the solute content in the Al matrix increases while the amounts of nonequilibrium second phase decreases. 3) Nonequilibrium second phase is limited the primary dendrite arm spacing in the later stages of solution treatment. 4) The dissolution time of nonequilibrium second phase is propertionated the square of primary dendrite arm spacing.

Al-Mg 系合金의 應力腐飾龜裂에 관한 硏究

徐昌濟,林炳鎰 成均館大學校 1982 論文集 Vol.31 No.-

Stress corrosion cracking(S.C.C), which was tested in one mole Nacl and 0.9% H_2O_2 solution by loading 90% of 0.2% proof stress on 5,6,7,8 and 10% Mg alloys was investigated and the results are as follow. 1) with increasing of Mg content in Al-Mg alloy, hardness, ultimate tensile strength, proof stress and S.C.C. Susceptibility increased, while elongation decreased. 2) stress corrosion susceptibility was reached to maximum value during the aging and by short time aging with being proportional to increasing of Mg content 3) stress corrosion susceptibility took place earlier than maximum hardness value and the difference was attributed to by variational precipitation behavior. 4) It was though that Al 8% Mg alloy was good for stress corrosion cracking

Cu-base合金의 Boron化에 의한 表面改質

徐昌濟,文貞勳,林秉守,朴洙用 成均館大學校 科學技術硏究所 1993 論文集 Vol.44 No.1

Boriding has been investigated by means of a surface heat treatment burying in amorphous boron powder under an argon gas atmoshere. The hardness of the boronized surface on the Ag and Cu alloys show the range of Hv 600 to Hv 1000 depending on chemical compositions. Moreover, in order to investigate the effect of each alloying element in pure Cu on increase in boronized surface hardness, various Cu-binary alloys, which contained Mn, Ti, Si, Zn or Al element, were boronized. The boronized surface of the alloys has been investigated from metallographic and X-ray analyses and hardness distribution.

Al-8%Mg 合金의 機械的 性質에 미치는 加工熱處理의 影響

徐昌濟 成均館大學校 科學技術硏究所 1984 論文集 Vol.35 No.1

The tensile and toughness tests were made on the Al-8%Mg alloy aged at 200℃ for various periods after aging at 150℃ for 24 hr followed cold rolling by 0, 30 and 50%. Behaviors of micro-shrinkage during rolling were correlated mechanical properties. Rolling in the reduction ratio from 30%, or more ensured a satisfactory repairing effect on the micro-shrinkages and good properties. The two step aging is not effective, but the thermo-mechanical treatment is effective in strengthening; of the alloy. The effect of theromo-mechanical treatment is due to synergetic effect of refining the structure of precipitates and presence of dislocations.

Al系 合金의 熔接性에 관한 硏究

徐昌濟 成均館大學校 科學技術硏究所 1987 論文集 Vol.38 No.1

A study was made of the effect of filler metals on the weldability of Al-Zn-Mg and Al-Zn-Mg-Cu alloys, using TIG welding methode. The filler metals were A4043 and A5356 alloys. The results obtained from this study are summarized as follows. 1. In the same base metal, the tensile property and charpy impact value of welds made with A5356 filler metal are higher that of A4043 filler metal, and in the same filler metal Al-Zn-Mg alloy is higher than that of Al-Zn-Mg-Cu alloy. 2. It is considered that the phenomenon of hardness recovery in heat affected zones by natural aging results from G.P zone formation. 3. It is considered that softening in heat affected Zones results from the difference in vacancy concentration after welding. 4. It is considered that the difference of aging behavior in heat affected zone results from precipitates for pre-heat treatment condition.

AA 7075 Al 합금용접부의 응력 부식 균열에 관한 연구

서창제 成均館大學校 科學技術硏究所 1988 論文集 Vol.39 No.1

An investigation was made on the effect of microstructure on the stress corrosion cracking(SCC) in 3.5% NaCl solution for Al-Zn-Mg-Cu series 7075-T6 welds. SCC of welds occurrs at the HAZ about 7 mm far from the fusion boundaries regardless of applied stress. In this region, hardness is low and peak temperature on welding rises up to about 300℃. In the matrix of this region, G. P. zone and η'phase partly dissolute or coarsening of η' phase and precipitation of η phase occurrs on welding. The grain boundary precipitates of this region are closely spaced and continuously formed along grain boundary. Preferential dissolution of these g.b precipitates plays an important role in initiation and propagation of SCC.