한국주조공학회

Retained austenite in matrix of austempered ductile iron has been well-known as a parameter in controlling mechanical properties, but investigation to obtain quantitative relationship with mechanical properties lack. Therefore, this study executed austempering treatment at various temperatures on ductile iron alloyed with Mo, Ni, Cu. In consequence, microstructure of retained austenite transformed coarse, and quantity increased according as austempering temperature increased. After heat-treatment, microstructure of specimen alloyed with Ni was fine, and toughness improved. At austempering temperature up to 400℃, carbide precipitation started in retained austenite. In consequence, afforded cause of hardness increase, a lot of increase did not arise for coarse structure.