Evolution of microstructures of hypoeutectic white cast iron ingots by rheocasting

An investigation was made on the evolution of microstructures of hypoeutectic white cast iron ingots containing 2.5% carbon and 1.8% silicon produced by rheocasting in which the solidifying alloys were vigorously agitated by electromagnetic stirrer during isothermal cooling and continuous cooling processes. The results show that for proper agitating temperatures and speed, dendrites are gradually evolved into global structures for certain agitating time. The isothermal cooling process can be divided into two stages, i.e. 1523 K which is 20 K lower than the temperature of liquidus of the alloy and 1483 K which is 54 K higher than the temperature of solidus of the alloy. The dendrites are bent and gradually changed into separated particles and global structures in the end of isothermal cooling process. Grain clustering is observed when isothermal temperature or agitating speed decreases abruptly. Dendrite fragments are found in continuous cooling process.