Fracture Mechanism of Ferritic Ductile Iron under Instrumented Impact Load at Low Temperatures

The impact toughness of 400-18L ductile iron (FCD400-18L) was measured by V-notch Charpy impact test at room and low temperatures. SEM and TEM were used to analyze the fracture mechanism. Experimental results show that the energy absorbed by impact test decreases significantly with the decrease of temperature. The fracture properties were measured using instrumented impact testing at temperatures between –80 and 20°C. The total impact fracture energy, the crack initiation and propagation energy, the dynamic loads and the ductile to brittle temperature were measured. The 400-18L ductile iron exhibited much higher resistance to ductile fracture at high test temperatures, while its resistance to brittle fracture at low test temperatures was reduced. The fracture morphology analysis was discussed in terms of the two fracture types: ductile fracture mechanism upon the BDTT (brittle to ductile transition temperature) and brittle fracture mechanism below the BDTT.