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

Design of the austempering heat treatment of a ductile iron differential case aided by computer simulation

“…Furthermore, this behavior was considered to be temperature-dependent. Based on the work of Boccardo et al (2017b), the relation between the stress  and total strain e is given by the constitutive law defined as:…”

“…The phase volume fractions are computed with the metallurgical model described in Section 2.2. The temperaturedependent phase densities are calculated as in Boccardo et al (2017b). For the thermal problem, the heat released or absorbed by phase change is considered (Boccardo et al, 2017b).…”

“…The temperaturedependent phase densities are calculated as in Boccardo et al (2017b). For the thermal problem, the heat released or absorbed by phase change is considered (Boccardo et al, 2017b). The heat transfer equation is written as follows:…”

“…Moreover, information regarding model application, such as part modeling (initial and boundary conditions, domain discretization) and metallurgical model setting (employed data base or fitting technique) is rather scarce. Boccardo et al (2017b) proposed a thermo-mechanicalmetallurgical model for the three-step austempering heat treatment, considering the reverse eutectoid, ausferritic, and martensitic transformations; the modeling involved the microscale in order to consider the microstructure features of the ductile iron, such as graphite nodule size, shape and dimension of the growing phases, heterogeneous carbon concentration within the matrix, among others. This model allows predicting a final martensiticausferritic matrix and the final dimensional change of the part.…”

“…In order to do that, the general-purpose software ABAQUS is employed to solve the thermal and mechanical problems at a macroscale by means of the finite element method. The metallurgical problem is solved by taking into account the microscale features of the material by a novel model previously published and validated by the authors (Boccardo et al, 2017b), which is here implemented into ABAQUS and coupled with its thermo-mechanical model by means of user-defined subroutines.…”