Development of a microstructural cohesive zone model for intergranular hydrogen environmentally assisted cracking

During the initial stages of hydrogen environmentally assisted cracking (HEAC), including crack incubation, initiation and microstructurally short cracking, the geometrical configuration of the microstructure greatly influences the crack growth behaviour. Therefore, there is a big incentive to generate a model which can replicate intergranular HEAC at a microstructural scale. This report provides a general framework to implement a microstructural intergranular HEAC model by using a cohesive zone approach in Abaqus. The parameters of the phenomenological model were fitted by using in-situ synchrotron tomography observations of crack initiation and propagation during HEAC of AA7449-T7651. After fitting the parameters, the real HEAC behaviour of the aluminium alloy 7449-T7651 has been replicated accurately. Several characteristic HEAC features were achieved, including crack segmentation, preferential cracking along grain boundaries with a high resolved normal stress and cracks slowing down at grain boundary triple junctions. Comparisons with experimental observations show the suitability of this approach for the prognosis of crack initiation and propagation at a microstructural scale under HEAC conditions.