Cast iron with magnesium induced spheroidised graphite

Cast iron is a brittle material and it is advantageous to process it in such a way to improve its ductility. The brittleness is partially due to the graphite flakes which act as nucleation sites for cracks. Therefore it is an advantage to have the graphite present as spheres. This can be achieved by a heat treatment regime or by the addition of a small amount of Mg which poisons the graphite growth directions