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低濃度 Al-Si系合金에 있어서의 Si 析出物의 粗大化 現象
趙顯麒,李基大,崔德淳 慶北大學校 1981 論文集 Vol.31 No.-
The coarsening behaviours of Si precipitates in dilute Al-Si alloys havs been investigated by means of scanning electron microscopy and also determined the number density of Si precipitates and activation energy for the growth of precipitates. The mean radius of Si precipitates in dilute Al-Si alloys was proportional to (time)^(1/3) and this results agree with Lifshitz-Wagner theory for the diffusion controlled mechanism. The number density of Si precipitates was decreased monotonously with increasing of ageing time. Activation energies for the coarsening of Si precipitates in Al-0.8wt% Si alloy and Al-1.2wt%Si alloy were 33.44 Kcal/mol and 32.9 Kcal/mol respectively, which agreed with that of inter-diffusion.
김종대,최덕순,이주완 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.11
A Pure and doped Mo wire were fabricated by direct current sintering and swaging. The specimens were annealed at various temperature and investigated mechanical properties, recrystallization temperature and bubble formation mechanism by EDAX. The bubble rows which were existed in doped Mo wire enhanced the mechanical properties and recrystallization temperature. It was considered that complex oxide of Al, K and Si components was contributed to the bubble formation.
금속산화물 (W, Fe, Cr-Oxide) 의 In-Flight Plasma 에 의한 환원
김종대,김동의,최덕순 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.12
The oxides of tungsten, iron, chromium are very strong carbide forming elements, therefore, it is a very useful method that their oxides are reduced by carbothermic In- Flight Plasma reduction. The experimental apparatus in the present study used a secondary nozzle and an electromagnet so that the plasma flame could rotate in the secondary nozzle. The variables of experiment were the amount and the sort of the reductants, size of feeding materials and the powder feeding rate. The reduced particles were collected in water cooled pipe and paper filter. By increasing the reductant ratio and the reduction ratio the fixed carbon content and free carbon content were increased. By increasing the powder feeding rate and the size of feeding material the reduction rates were decreased. The reduction rate of WO_(2.9) Fe₂O₃and Cr₂O₃were 80%, 90% and 20%, respectively, by the in-flight plasma process. The reduced particle size were below 0.03㎛ ; therefore, an ultra-fine powder could be obtained by the present in-flight plasma process.
이종현,원창환,최덕순,고석권 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.9
The experimental results for the fabrication of(W·Ti)C powder by self-combustion reaction are summerized as follows : 1) The reaction parameter to influence greatly in synthesis of (W·Ti)C powder is the mole ratio of each elements. Excess carbon must be added to control the final composition because of the carbon deficiency during the reaction. Experimental results show that the optimum mole ratio of W, Ti and C is 0.2, 0.7, and 1.2 respectively. Self-combustion is difficult with increasing the carbon mole ratio compared with the stoichiometry and the steady state combustion is not occurred. 2) In case that the mole ratio of Ti to W is large, combustion is impossible due to decreasing of adiabatic reaction temperature. Adiabatic reaction temperature of(W·Ti)C is about 2900 to 3000°K and the steady state combustion at this temperature is performed. 3) The particle size and the compression density of W powder are constant regradless of the reaction products. However, the reaction rate decreases with increasing the particle size. The reaction rate increases with the compression density of W powder and is constant above that of 2.77 g/㎤.