Austempering heat treatment of ductile iron: Computational simulation and experimental validation

Abstract

The three-step austempering heat treatment of ductile iron parts in this paper is simulated by employing acoupled thermo-mechanical-metallurgical model. The thermo-mechanical formulation is solved in the macroscaleusing the finite element method to predict the evolution of temperatures and deformations in the wholepart. The metallurgical model deals with phase transformations that occur during the heat treatment, which areanalyzed in the microscale. For each phase transformation the microstructure features such as type,distribution, and shape and size of phases are considered employing representative volume elements. Theperformance of the proposed model is tested by simulating experimental heat treatments reported in theliterature. By means of comparison with experimental results, the model proved to be able to predict correctlythe evolutions of temperature and dimensional changes, the minimum austenitization and austempering times,and the final phase fractions. It is concluded that this model could be a useful computational tool in the designof austempered ductile iron parts as well as the austempering heat treatment process.