MONITORING FATIGUE DAMAGE IN HYPOEUTECTIC AL-SI CASTINGS WITH VARYING MICROSTRUCTURE CHARACTERISTICS [Keynote]

Due to their low density, good recyclability and producibility of complex net shapes, cast aluminium alloys are promising candidates for many demanding applications in mobility, power generation and machinery. The inherent microstructure inhomogeneity is the most striking challenge in placing cast Al alloys in cyclically loaded components. Therefore, obtaining a quantitative understanding of the correlation between casting process, microstructure parameters (dendrite arm spacing (DAS), size and shape of (i) the eutectic silicon, (ii) the gas porosity, and (iii) the shrinkage porosity) and fatigue properties (fatigue limit, fracture mechanical data) is the aim of the present study. The adjustment of these microstructure parameters by tailored casting systems and fatigue testing revealed that the fatigue limit increases and the threshold of the stress intensity range Delta K th decreases with decreasing DAS (microstructure refinement). Microscopic in-situ-tracking of fatigue damage yields a detailed understanding of the fatigue mechanisms that will be the basis of a numerical short crack modeling approach in the future.
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