Influence of Graphite Degenerations on Mechanical Properties of Ductile Iron

Ductile iron - also known as spheroidal graphite iron (SGI) - is a versatile material that exhibits a wide range of applications. In addition to the matrix structure itself, graphite morphology and material defects, such as graphite degenerations, also have a decisive influence on its mechanical properties. Missing or incomplete classifications of these deviating graphite morphologies in common standards, alongside insufficient knowledge regarding their effects, leads to a more complicated lifetime assessment and often results in rejection of SGI components. Therefore, relevant material parameters were derived from experimental quasi-static and fatigue investigations on SGI materials with different graphite degenerations and correlated with microstructural parameters quantified by an optimized digital image analysis method. While a linear correlation between the amount and mechanical properties was identified for spiky graphite, for chunky graphite, the presence in general can lead to a detrimental reduction in mechanical properties.