In Grey Irons mechanical properties are dominated by the form, amount and distribution of the graphite flakes giving relatively low tensile strengths of 150-400 MPa with very little ductility. In contrast, strength levels of 400-1200 MPa or more are obtained in correctly treated Ductile Irons since their mechanical behaviour depends essentially upon the nature of their matrix structures. As illustrated in Fig.1, in Ductile Iron there is no graphite network to provide an easy fracture path and the full mechanical strength and ductility of the matrix is realised.
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