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

This work is focused on the micromechanical modelling of the low-cycle fati gue of the nickel-based gamma-gamma superalloy AM1 at high temperatures. Th e 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 t he applied and internal stresses. The latter are split into two contributio ns, misfit stresses and compatibility stresses between the elastic gamma' p hase and the elastoplastic gamma phase, which are estimated within a simpli fied composite approach. Internal stresses may induce slip activity and/or be relaxed by it, which results in a complex sequence of slip activation ev ents in the different channels under increasing applied stress. The conside ration of these effects leads to a prediction of the nature and distributio n of the active slip systems within the channels in [001] tension and compr ession and during low-cycle fatigue. The resulting microstructural behaviou r and its consequences regarding the anisotropic nature of the coalescence of the gamma' precipitates are discussed with respect to the available expe rimental data.