Impact Toughness of Compacted Graphite Iron Containing Sn Used for Brake Drums

The impact toughness and impact fracture morphology of compacted graphite iron(CGI) containing Sn were investigated.The results show that Sn mainly solidly dissolved uniformly in the matrix but distributed less in the graphite.With the increase of Sn content,the impact toughness of CGI firstly increased and then decreased,and when the mass fraction of Sn was 0.057%,the impact energy was the highest,up to 9.11 J.The impact fracture of the CGIs containing 0.003% Sn and 0.121% Sn showed typical cleavage fractures and river patterns.Free cementite and bulk vermicular graphite were supposed to be the initial origins of cracks.Fracture of the CGIs containing 0.028% Sn and 0.057% Sn exhibited quasi-cleavage patterns and no cleavage facets were found.Appropriate Sn content helps to increase the impact toughness of CGI but excessive Sn speedily damages the impact toughness.