Effect of Cooling Rate on the Solidification Behavior and Microstructure of SiC_w/Al-18Si Composites

• 作 者: 耿林 魏红梅
• 机 构: School of Materials Science & Engineering,Harbin Institute of Technology,
• 出 处: Journal of Wuhan University of Technology(Materials Science
• 发表日期: 2009年S1期
• 关键词: stick eutectic equiaxed squeeze solidification refined coherent refinement nucle

Al-18Si alloy reinforced with 15%,20% and 25%(volume fraction) SiC whiskers were prepared by squeeze casting technique and the solidification behavior and microstructure of as-prepared composites at different cooling rates were studied by DSC,optical microscope,SEM and TEM.The results show that silicon phase is nucleated on SiC whiskers.With the increase of cooling rate,the degree of undercooling increases in the composites as well as in the alloys.The increase of cooling rate leads to a reduction in the size of eutectic Al-Si and also changes its morphology from short stick to equiaxed.However,the change of primary Si is complex.The primary Si size is refined,and then coarsened with increasing cooling rate.The primary Si morphology of composites changes from agglomerate to stick.

Al-18Si alloy reinforced with 15%, 20% and 25% volume fraction SiC whiskers were prepared by squeeze casting technique and the solidification behavior and microstructure of as-prepared composites at different cooling rates were studied by DSC, optical microscope, SEM and TEM. The results show that silicon phase is nucleated on SiC whiskers. Due the increase of cooling rate, the degree of undercooling increases in the composites as well as in the alloys. increase of cooling rate leads to a reduction in the size of eutectic Al-Si and also changes its morphology from short stick to equiaxed. However, the change of primary Si is complex, and then coarsened with increasing cooling rate. The primary Si morphology of composites changes from agglomerate to stick