FRACTURE TOUGHNESS AND FATIGUE FRACTURE OF RARE EARTH-MAGNESIUM NODULAR CAST IRON

The endurance of rare earth-magnesium nodular cast iron to fracture under static and dynamic loads is shown to be more accurately represented by the parameters of fracture mechanics rather than by impact toughness. Parameters such as K_(Ic), da/dN and AK_(th) are represented. With a view to clarifying the effect of various metallographic structures upon the fracture toughness of the material, the rate of spheroidization, the morphology of graphite, the size of spherulites, the matrix structure, etc. were separately examined. At the same time, crack propagation characteristics for different stages of fatigue fracture were also investigated. It is recommended that nodular cast iron could be in greater strength and better toughness provided that its microstructure is improved.