Compacted and spheroidal graphite irons: experimental evaluation of Poisson’s ratio

Spheroidal Graphite cast Iron (SGI), also known as ductile iron, represents a perfect material for a very large range of modern applications. It is successfully used wherever optimal strength, stiffness and even low costs are required: high values of tensile strength and Young’s modulus are between its most appreciable proprieties. At the same time, nowadays, a different cast iron, known as Compacted Graphite Iron (CGI) or vermicular graphite iron, is moving the first steps in replacing SGI respect to some specific applications. It depends on a better castability, machinability and thermal resistance. CGI is an ideal cast iron in the case of components under simultaneous mechanical and thermal loadings, such as cylinder blocks and heads. Unfortunately, while SGI benefits of a wide scientific literature, CGI is a relatively unknown material. Moreover, since its particular microstructure, the production of CGI presents additional difficulties and it is not easy to obtain a stable proprieties in the CGI alloy. This paper illustrates a way for the experimental evaluation of the Poisson’s ratio by tensile specimens, comparing this propriety in the case of SGI and CGI.