Phenomenon of high extension observed in grey cast iron after micro-rolling

Abstract

Grey cast iron is traditionally thought to not deform plastically, because of the presence of a large number of graphite flakes, which act as crack initiation sites. Therefore, researchers had given up efforts to study its formability. However, our research suggests that, when the thickness of grey cast iron samples is decreased to 400μm, they can be elongated by cold rolling, with the extension being as high as 156%, which is well beyond the forming limit of grey cast iron. This phenomenon confirms that the plasticity size effect occurs in thin grey cast iron samples, breaking the ceiling of their intrinsically low plasticity. We use classical plasticity theory and the surface-layer ratio theory to investigate the mechanism responsible for the deformation that occurs during micro-rolling. We also propose a method for improving the plasticity of extra-brittle materials.