This study intends to add fixed contents (~2.0wt%) of solid solution strengthening elements silicon and nickel to spheroidal graphite cast iron with low silicon content (~2.1wt%) to explore
the effect of silicon and nickel on spheroidal graphite cast iron, that the influence of the degree of aggregation of magnesium-containing inclusions in the cast iron in the eutectic cell boundary regions, and the effect of the degree of clustering of magnesium-containing inclusions caused by these two elements on the thermal cycle of ferritic spheroidal graphite cast iron induced intergranular embrittlement. The experimental results show that the addition of silicon and nickel will increase the degree of clustering of the inclusions in the eutectic cell boundary regions. The room temperature elongation of spheroidal graphite cast iron tends to decrease with the addition of silicon and nickel, and its extension at 400℃ The deterioration rate of elongation after thermal cycling also increases with the addition of silicon and nickel. In addition, according the observation of the tensile fracture surface morphology after thermal cycling, the fracture surface morphology of the low silicon content (~2.1wt%) specimen after 150 thermal cycles is still dimple ductile fracture, but the silicon or nickel addition specimens with the increase of the number of thermal cycles, the fracture morphology of the dimple fracture morphology or cleavage fracture morphology changed to the morphology of the intergranular embrittlment fracture surface.
Keywords: Ferritic spheroidal graphite cast iron, Solid solution strengthening element embrittlment, Thermal cycling induced intergranular fracture