Low-cycle fatigue of a nickel-based superalloy at high temperature: Simplified micromechanical modelling
Abstract
This work is focused on the micromechanical modelling of the low cycle fatigue of the nickel based γ/γ' superalloy AM1 at high temperature. The nature of the activated slip systems in the different types of channels of the γ phase is analysed, taking into account the combined effects of the applied and internal stresses. The latter are split into two contributions, misfit stresses and compatibility stresses between the elastic γ' phase and the elasto-plastic γ phase, which are estimated within a simplified composite approach. Internal stresses may induce slip activity and/or be relaxed by it, which results in a complex sequence of slip activation events in the different channels under increasing applied stress. The consideration of these effects leads to a prediction of the nature and distribution of the active slip systems within the channels in [001] tension, compression and during low cycle fatigue. The resulting microstructural behaviour and its consequences regarding the anisotropic nature of the coalescence of the γ' precipitates are discussed with respect to the available experimental data.