Microstructure and grain size of AlSi7Mg alloy billet prepared by semi-continuous casting at low superheat

which was reheated at different heating temperatures and holding time

were observed by optical microscope and image analyzing software to understand microstructure evolution and grain growth during reheating process combining with differential scanning calorimetry（DSC） . The results reveal that microstructure evolution is closely related with reheating temperature and holding time. With increasing in heating temperature and holding time

grain is grown spherically

and microstructure evolution is faster and faster with increasing in heating temperature. Grain is grown more and more spherically with extending in holding time. The AlSi7Mg alloy billets with homogeneous and spherical as well as fine structure can be prepared by effectively controlling reheating temperature and holding time.