Jorge Rafael Velayarce(1),*, Christian Motz(1)
(1) Chair of Materials Science and Methods (MWW), Saarbrücken, Germany
*email@example.com, Tel: +49 681 3025043
Fatigue is one of the leading causes of failure in many engineering components. The recent growing interest in small scale materials for micro-electro-mechanical systems have raised new questions regarding the physical-size influence on fatigue. As the scale is in the range of typical fatigue dislocation structures, i.e. persistent slip bands (PSBs), size limitations on the formation of PSBs, cell structures and the initiation of fatigue cracks at grain boundaries (GB) are some of the relevant questions to be answer.
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 bicrystalls 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 provides 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 under full load reversal in order to study the influence of the sample size, crystal orientation, the dislocation density and grain boundaries on the PSBs, cell structures and damage morphology.
Figure 1. Backscattered electron and kernel average images of single and bi-crystalls after micro-fatigue tests