In this research, the effect of semi-solid isothermal heat treatment on microstructure, hardness and impact toughness of ductile iron (DI) is studied. Heat-treated air-cooled ductile iron shows spheroid graphite, cementite and fine pearlite matrix structure. At the early stages of heating time (up to 20 min), the DIs show significant decrease in amounts of graphite and significant increase in amounts of cementite. By increasing heating time, above 20 min, the DIs show slightly decrease in amounts of graphite and slightly increase in amounts of cementite. Hardness values increase by increasing heating time. Meanwhile, the impact toughness decrease with increasing heating time. The optimum heating treatment condition for reasonable structure and mechanical properties could be achieved at the temperature of 1165℃ for the heating time range of 10 to 15 min.
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http://dx.doi.org/10.1016/j.msea.2006.07.108
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