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전자교반에 의한 Al 합금의 초정입자 미세화에 관한 연구
임성철,윤의박 ( Sung Chul Lim,Eui Pak Yoon ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.5
N/A The change of microstructure of Al-7wt%Si alloy was examined by using a induction motor of 3-phases and 2-poles in semi-solid electromagnectically stirring process. The size and degree of sphericity of primary solid particles were observed by means of change of cooling rate. At a certain cooling rate, the size of primary solid particles increased and the sphericity became perfect, as the fraction of solid increased. The average size of primary solid particles was 43㎛ when the fraction of solid was 0.3 and at 600℃, input voltage 140V, cooling rate 2.5℃/s. It was shown that the size of primary solid particles was proportional to local solidification time.
전자교반시 미세화제첨가에 따른 Al-7wt%Si 합금의 미세조직변화
임성철,윤의박 ( Sung Chul Lim,Eui Pak Yoon ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.5
N/A To gain a semi-solid alloy the electromagnetic stirring by an induction motor of 3 phase and 2-poles was used. And it was also observed that the change of primary particle size, distribution and degree of sphericity by addition of a refiner, Al5Ti1B. The effect of refiner on the distribution and dimensions of primary particles prior to that electromagnetic refining on those was examined. In case of electromagnetic stirring with the refiner Al5Ti1B, the average size of primary solid particles increased as the fraction of solid increased. However it decreased as the amount of Al5Ti1B addition increased to 0.5% and then it was increased again as the addition amount of Al5Ti1B increased above 1.0%. The average size of primary solid particles was 31㎛ in case of melt temperature 600℃ when the fraction of solid was 0.3, input voltage 140V, cooling rate 2.5℃/s, and 0.5% Al5Ti1B. To use the electromagnetic stirring with the addition of a refiner was able to obtain more small primary solid particles than to use the electromagnetic stirring only.
전자교반시 Al-7wt%Si 합금의 초정입자에 미치는 유동의 영향
임성철,윤의박 ( Sung Chul Lim,Eui Pak Yoon ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.6
N/A In this study, to gain the semi-solid alloy we employed the electromagnetic rotation by a induction motor of 3-phases and 2-poles for Al-7wt%Si alloy and observed the size of primary solid particle, distribution state of primary solid particle, the degree of sphericity, and fraction of primary solid for the evaluation of its results. The size of primary solid particle increases from 98㎛ to 118㎛ as solid fraction increases from 0.2 to 0.5. The degree of sphericity increased as the solid fraction increased. Solid particles obtained from the microstructures of isothermally held sample were coarsened and the degree of sphericity was enhanced as isothermal holding time increased. However, when the sample was stirred for more than 40min, solid particles merged together and liquid phase was entrapped within the cluster of solid particles. The size of primary solid particle was not changed significantly with the variation of input voltages by 160V over which solid particles began to merge together to be a large cluster of about 170㎛ at 180V. The standard deviation and the degree of sphericity were not changed significantly with the variation of input voltage.
이종춘,임성철,윤의박 ( Jong Chun Lee,Sung Chul Lim,Eui Pak Yoon ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.1
N/A Electromagnetic stirring was applied as a treatment method of semi-solid state processing. The study on the change of the microstructure of Al-4.5wt%Cu alloy was conducted through the size of primary solid particle and its sphericity in various stirring conditions. First, we produced a rotating magnetic field type, electromagnetic stirring apparatus having 3-phases, 2-poles and common frequency of 60㎐(inner diameter of core : 191㎜;height of core : 225㎜). The apparatus specified that the magnetic flux density was about 0.05T at the center when maximum power was loaded. Microstructures obtained by electromagnetic stirring treatment were mixed morphology which consisted of primary solid particles and fine eutectic phases caused by the quenching effect of remaining liquid phase. The shapes of primary solid particle were rosette type or spheroid type and the effect of electromagnetic stirring on molten alloy as the stirring method of semisolid state processing was confirmed.
과공정 Al-Si 합금에서 초정 미세화 및 공정 Si 의 개량화에 관한 연구
이태호,임성철,김정호,이창희,윤의박 ( Tae Ho Lee,Sung Chul Lim,Jeong Ho Kim Chang Hee Lee,Eui Pak Yoon ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.4
N/A Hypereutectic Al-Si alloys have many advantages such as excellent wear resistance, high ratio of strength to density, good castability (esp. fluidity) and elevated strength. However, in casting process, the segregation of coarse primary Si and flake eutectic Si decrease mechanical properties. In this study, using AlCuP refiner and Sr modifier, it is intended to obtain simultaneous effects of refinement of primary Si and modification of eutectic Si in hypereutectic Al-Si alloys, to measure hydrogen gas contents and to evaluate mechanical properties. Experimental results show that in the case of simultaneous effect of refinement of primary Si and modification of eutectic Si, two step addition that modifier is added into melt after refiner addition at 750℃ is more effective than simultaneous addition of modifier and refiner at 750℃ in terms of microstructure and hydrogen gas control. All mechanical properties tested were found to be improved by refinement of primary Si and modification of eutectic Si.
김정식,김동희,이창희,윤의박,임성철 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.4
Experiments were performed by thermogravimetric(TG) technique for A356.2(Al-7Si-0.4Mg) aluminum alloy containing 0.4wt%Mg to examine the effect of magnesium on the oxidation kinetics in dry and moist air over the temperature range of 200∼550℃. The results of TG analysis showed that oxidation in moist air was much faster than in dry air at high temperatures above 525℃ while oxidation in both dry and moist air below 200℃ was stagnant. For the surface analysis of oxidation, the results of Auger electron spectroscopy(AES), X-ray diffraction patterns(XRD), analysis showed that only aluminum oxide was formed at relatively low temperature of 300℃ while the duplex film structure of Mg oxide/Al oxide/matrix was formed at high temperature of 550℃. MgO was a major constituent on the surface of oxide film, but the relative concentration of MgO decreased with increasing depth, while that of spinel, MgAl₂O₃ increased.