Constitutive modeling of a directionally solidified nickel-based superalloy DZ125 subjected to thermal mechanical creep fatigue loadings

A transversely isotropic continuum elasto-viscoplasticity model, which was developed from Chaboche's unified constitutive model, was formulated to capture the thermal mechanical creep fatigue deformation behavior of a directionally solidified nickel-based superalloy. A fourth-order tensor was introduced to model material anisotropy. In order to model the tertiary creep behavior, the Kachanov damage evolution equation was coupled into the stress tensor. Based on the test results of uniaxial tensile, fatigue, and creep loadings at isothermal temperature conditions, the material parameters are obtained. Thermal mechanical fatigue (TMF) and creep-fatigue interaction test results were used to verify the robustness of the model. Additionally, strain-temperature-dependent stress-strain responses under TMF loadings were analyzed using the present model. Under strain-controlled conditions, both of the stress ranges and mean stresses are strongly influenced by the strain-temperature phases, a key parameter for TMF tests.