Effects of Casting Conditions and Additions of Sr and Ti＋B on Solidification Structures of Recycle Al-Si-Cu System Cast alloys = 리사이클용 Al-Si-Cu계 주조합금의 응고조직에 미치는 Sr 및 Ti＋B 첨가와 주조조건의 영향

다국어 초록 (Multilingual Abstract)

The effects of cooling rate and additions of Sr and Ti-B on microstructural features such as grain size, dendrite arm spacing, morphologies of eutectic silicon and iron rich compound were investigated for the Al-6.55%Si-2.78% Cu-0.59%Fe-0.38%Mg-0.34%Mn alloy of ACAB type. This alloy solidified in the order of primary α, a+a-AlFeMnSi compound eutectic, α+Sieutectic, α+β-AlFeMnSi. a +Si+Mg₂Si and α+Si+Al₂Cu eutectic. The grain size, dendrite arm spacing, the size of eutectic silicon particles and the length of needle like β-AlFeMnSi decreased with increasing the cooling rate, and they were in linear relations on logarithmic scales. Addition of small amount of Ti-B remarkably refined grain size while it practically unaffected the other solidification structures At the cooling rate of 2.73K/s, 14.38K/s and 108.08K/s, the eutectic silicon crystals fully modified by adding Sr more than 60ppm, 20ppm and 5ppm, respectively. Addition of Sr and higher cooling rate tended to modify the needle like iron rich compounds to Chinese script type one. DSC analysis revealed that the Sr modification was accompanied by the characteristic changes in cooling curve.