Creation of nanostructured Austempered Ductile Iron (ADI) by a novel process

CREATION OF NANOSTRUCTURED AUSTEMPERED DUCTILE CAST IRON (ADI) BY A NOVEL PROCESS By Saranya Panneerselvam, Susil Putatunda Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, MI ABSTRACT Austempered Ductile Cast Iron (ADI) has emerged as an important engineering material in recent years because of its excellent combination of mechanical properties such as high strength with good ductility, good fatigue strength and fracture toughness together with excellent wear resistance. These combinations of properties are achieved in ADI as a result of a unique microstructure consisting of acicular ferrite (α) and high carbon austenite (γHC). Refining of this microstructure in the nano scale region could possibly further enhance the mechanical properties of ADI. In this investigation, nanostructured austempered ductile cast iron (ADI) consisting of bainitic ferrite and high carbon austenite. This was achieved by applying a unique process consisting of austenitization and simultaneous high temperature plastic deformation (at the same austenitizing temperature) followed by austempering process. The influence of plastic deformation on the microstructure and mechanical properties of nanostructured ADI has been examined. The effect of two-step austempering on the microstructure and mechanical properties was also investigated. Test results indicates that the application of high temperature plastic deformation together with austempering can result in nanostructured grains in ADI. The extensive transmission electron micrographic investigation further established the presence of nanoscale size grains in ADI as a result of the application of the unique process.