Effect of withdrawal rate on microstructure of a hypoeutectic Al-Si alloy by low superheat DC casting

作     者：Zhao Dazhi Liu Fang Yu Fuxiao Hong Tao Zuo Liang 

作者机构：Department of Metal Forming School of Materials and Metallurgy Northeastern University Key Lab. for Anisotropy and Texture of Materials (Ministry of Education) Northeastern University Xinjiang Joinworld Co. Ltd. 

出 版 物：《China Foundry》 (中国铸造（英文版）)

年 卷 期：2013年第10卷第3期

页      面：172-175页

核心收录：

学科分类：080503[工学-材料加工工程] 080603[工学-有色金属冶金] 08[工学] 0806[工学-冶金工程] 0805[工学-材料科学与工程（可授工学、理学学位）] 0802[工学-机械工程] 080201[工学-机械制造及其自动化] 

基　　金：supported by the Postdoctoral Foundation of Northeastern University and the National High Technology Research and Development Program of China(Grant No.2009BAE80B01) 

主　　题：direct chill casting AlSi7Mg alloy withdrawal rate 

摘      要：To obtain the billet with homogeneous and spheroidized primary grains is the key step in the semi- solid forming process. Among the semi-solid billet preparation methods, the process of low-superheat direct chill （DC） casting is simpler and more effective. In this study, the billets of AISi7Mg alloy were prepared by low- superheat DC casting at various withdrawal rates. The effect of withdrawal rate on the surface quality of the billets was investigated, and the evolution mechanism of the microstructural morphology in the billets was analyzed. The results show that the periodic corrugations and a large quantity of fine shrinkage pits appear in the billet surface when the withdrawal rate is 100 ***-1, and the above defects in the billet surface can be eliminated completely when the withdrawal rate is above 150 ***-1. But when the withdrawal rate is too fast （250 ***-1）, the primary a grains, except the ones in the billet center, have not enough time for ripening due to the high silidification rate, and will solidify as the dendrite structure. When the withdrawal rate is between 150 - 200 ***-1, the dendritic growth of the primary a grains is effectively inhibited, and a billet of AISi7Mg alloy with a smooth surface and homogeneous, fine, non-dendritic grains can be obtained.