Effect of sample size and grain boundaries on the dislocation structures and damage evolution: A micro-fatigue investigationWednesday (26.09.2018) 17:00 - 17:15 S1/01 - A03 Part of:
Fatigue failure, one of the most investigated failure mechanisms, occur in a wide variety of engineering components. The recent growing interest in small-scale materials for sensors or actuators has raised new questions regarding the length scale influence on fatigue. As the scale is in the range of typical fatigue dislocation structures, size limitations on the formation of persistent slip bands (PSBs), cell structures and the initiation of fatigue cracks at grain boundaries (GB) are some of the relevant questions to be answered.
Grain boundaries are important planar defects providing substantial strengthening mechanisms in polycrystalline materials. However, due to elastic and plastic incompatibilities, additional stresses are created at grain boundaries, which could lead to slip transfer, fatigue crack nucleation, etc. Micron-sized bi-crystals can be employed to estimate local stresses and strains, which are associated with the stress-strain response, to get a better understanding of the role of GB. In situ micro-fatigue experiments not only provide information of microstructure and damage evolution but also of local stresses (Figure 1). On that account, our research focuses on cyclic fatigue of single and bi-crystalline micro-samples in order to study the influence of the sample size, crystal orientation and grain boundaries on damage morphology and dislocation structures.
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|Presentation||Figure 1||Fatigue damage morphology and dislocation structures of a bi-crystalline micro-sample with a grain boundary parallel to the cyclic loading direction.||215 KB||Download|