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Ca첨가 반응고 AZ31 마그네슘 합금의 재가열에 따른 미세조직 변화
김희경 ( Hee Kyung Kim ),성봉학 ( Bong Hak Seong ),반근호 ( Geun Ho Van ),김대환 ( Dae Hwan Kim ),성영록 ( Yeong Rok Seong ),임수근 ( Su Gun Lim ) 한국주조공학회 2012 한국주조공학회지 Vol.32 No.2
In this study, we are aimed to prevent grain growth of semi-solid AZ31 magnesium alloys during reheating process. The semisolid AZ31+(Ca) billets were investigated by using metallographic analysis, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy in order to elucidate the effect of Ca addition during reheating process. The grain growth of semisolid AZ31+(Ca) billet was reduced with increasing Ca content during reheating. The grain size of AZ31+(Ca) billet decreased with increasing volume fraction of Al2Ca particles. The grain growth rate constant K calculated by Oswald ripening LSW theory in AZ31+1.5wt.% Ca billet was the lowest 129.
반응고 Al-Zn-Mg계 합금의 반용융 압출을 위한 재가열 시 결정립 성장 억제에 미치는 Ca 첨가의 영향
박형원 ( Hyung Won Park ),김대환 ( Dae Hwan Kim ),심성용 ( Sung Yong Shim ),김희경 ( Hee Kyung Kim ),성봉학 ( Bong Hak Seong ),최창옥 ( Chang Ock Choi ),임수근 ( Su Gun Lim ) 한국주조공학회 2011 한국주조공학회지 Vol.31 No.6
There is thixo-extrusion to form high strength aluminum alloy. But, it is a problem that grains become grain coarsening during reheating process because the alloy was exposed at high temperature. In order to solve grain growth during reheating process, calcium was added in Al-Zn-Mg alloys. Primary a grain sizes of semi-solid Al-Zn-Mg-(0, 0.4, 0.6 and 0.9, wt.%)Ca were measured with image analyzer after reheating. Measured primary a grain sizes were applied to LSW(Lifshitz-Slyozov and Wagner) equation to check the effect of Ca on grain coarsening. Coarsening rate constant K values of semi-solid Al-Zn-Mg-(0, 0.4, 0.6 and 0.9, wt.%)Ca alloys were 371 mm3s-1, 247 mm3s-1, 198 mm3s-1 and 166 mm3s-1, respectively. As increasing calcium content, K value decreased which means grains are refined. Also, grains of calcium addition were more spherical than that of calcium free.