Microstructure and size of 6061 aluminum alloy semi-solid billets prepared by near-liquidus semi-continuous casting

which was reheated at different heating temperature and holding time

were observed by the Nikon E600POL optical microscope and image analyzer to investigate the formation of liquid phase

microstructure evolution and grain growth during reheating process combining with differential thermal analysis （DTA）. The results reveal that microstructural evolution is controlled by reheating temperature and holding time. With increasing in heating temperature and extending in holding time

grain is grown spherically and gradually

furthermore

microstructural evolution is faster and faster with increasing in heating temperature

and grain is grown more and more spherically with extending in holding time. The 6061 aluminum alloy semi-solid billets with homogeneous and round as well as fine structure can be prepared by effectively controlling reheating temperature and holding time.