Anisotropic Constitutive Modeling of a Single Crystal Superalloy at Elevated Temperature

Abstract

An anisotropic constitutive model based on crystallographic slip theory was formulated for nickel-base single crystal superalloys. The current equations include both drag stress and back stress state variables in the inelastic flow equation for slip in each slip system. Experiments were conducted to evaluate the need of back stress in the model. The test results showed the effect of reverse inelastic flow on unloading is orientation dependent, and that a back stress state variable in the inelastic flow equation is necessary for predicting the anelastic behavior. Model correlations and predictions with experimental data are presented for the single crystal superalloy Rene’ N4 at 760C and 982C.

Crystal Viscoplasticity of a Ni-Base Superalloy in the Aged State

“…Within the strain rate-sensitive temperature regime (T ! 750 C), most Ni-base superalloys become cyclically stable within a short period, as such five cycles are deemed sufficient to capture the stable response at a given strain rate [12]. For temperatures below 750 C where the cast high c 0 Ni-base superalloys are rate independent, conducting the experiment at a constant strain rate ð10 À2 ð1=sÞÞ until a stabilized hysteresis is obtained is acceptable.…”