Mathematical modelling of austempering by finite element method

Abstract

Austempered ductile iron (ADI) possesses a superior toughness than ordinary cast iron because the residual phase associated with bainitic ferrite is retained aust-enite instead of martensite or carbide. The desired micro- structure (devoid of pearlite, martensite or carbide) can be obtained provided the effective cooling rates at diff-erent cross-sections are accurately determinable for components with varying shape, composition and heat treatment requirements. In this study, a finite element model (FEM) has been developed to predict the temperature profile along different cross-sections following austeni-tizing at 870°C and austempering at 370°C. Solid bodies of different shapes have been meshed into hexahedron ele-ments by the present software. The o verall global matrix equation has been numerically solved by the Gaussian elimination method. Finally, it is found that the results predicted by the present model is in well accordance with the relevant experimental data on austemperability.