Environment-Assisted Crack Initiation in Aluminum Alloys Studied by Local Probe Techniques

Environment-assisted crack initiation in aluminum alloys is strongly related to the physical and chemical reactivity of intermetallic particles (IMPs) whatever their location, i.e., at grain boundaries or in the matrix. Therefore, this paper first focuses on the most recent contribution of microscale local probe techniques to the study of processes occurring at the coarse IMPs that need to be taken into account in the initiation stage of environment-assisted cracking (EAC). A critical review of microscale electrochemistry, chemistry, and analysis of the influence of stress on IMPs leading to the microscale analysis of crack incubation is presented. Moreover, the contribution of hydrogen to the initiation of EAC remains a widely debated issue. Therefore, the second part of this paper more specifically reviews and summarizes the contribution of some specific local probe techniques to a better understanding of the contribution of hydrogen enrichment to environment-assisted crack initiation. The remaining challenges in future studies needed to fully elucidate hydrogen-assisted cracking mechanisms at the microscale are discussed.