Low-cycle fatigue of a nickel-based superalloy at high temperature: simplified micromechanical modelling

摘要

This work is focused on the micromechanical modelling of the low-cycle fatigue of the nickel-based gamma-gamma superalloy AM1 at high temperatures. The nature of the activated slip systems in the different types of channel of the gamma 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 gamma' phase and the elastoplastic gamma 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 and compression and during low-cycle fatigue. The resulting microstructural behaviour and its consequences regarding the anisotropic nature of the coalescence of the gamma' precipitates are discussed with respect to the available experimental data. [References: 36]