Influence of silicon content on mechanical properties of IADI obtained from as cast microstructures

Abstract

This study investigates the mechanical properties of Intercritically Austempered Ductile Iron (IADI) obtained after the heat treatment of ductile irons having different as-cast microstructures and Si concentrations. Tensile strength, impact strength and hardness are measured. The results show that it is possible to obtain acceptable IADI microstructures starting from different as cast microstructures, obtaining similar mechanical properties than those obtained starting from fully ferritic matrices. Tensile strength, yield stress and hardness increase when the silicon content in the melt increases and with the amount of ausferrite present in the microstructure. Particularly, IADI achieved on 3.1% Si DI showing approximately 50% of ferrite and 50% of ausferrite have the best combination of mechanical properties. The IADI samples obtained using different chemical compositions and heat treatment parameters allowed to satisfy every grade specified in ASTM A536 standard for ductile iron showing improved elongation at failure.