Simulation of Non-Isothermal Mechanical Tests on a Single Crystal Nickel-Basis Superalloy

An extension of the constitutive viscoplastic model of Meric and Cailletaud is presented. The new model accounts for coupling of plasticity and viscoplasticity to describe the rate dependence at low and moderate temperatures. The model contains two boundaries: an elastic one and a viscoplastic one. Between the boundaries, the only contribution to yielding is the rate dependent viscoplastic mechanism. Once the viscoplastic boundary is reached, an additional rate independent flow mechanism becomes active. However, the extended model is not able to predict properly both creep and long-term relaxation tests simultaneously. Therefore, a deformation-induced softening is assumed, which is supposed to mainly affect static recovery. The model has been calibrated with the mechanical tests on a single crystal nickel-basis superalloy. The uniaxial tests have been carried out in the temperature interval 600°C – 1100°C in [001], [011] and [111] specimens. The predicted creep, relaxation and non-isothermal cyclic tests exhibit reasonable agreement with the experimental observations