MATEC Web Conf.
Volume 165, 201812th International Fatigue Congress (FATIGUE 2018)
|Number of page(s)||7|
|Section||High Cycle Fatigue, Fatigue at Notches|
|Published online||25 May 2018|
The significance of microstructure heterogeneities on the fatigue thresholds of aluminum castings
Institute of Materials Design and Structural Integrity, University of Applied Sciences Osnabrück, 49076 Osnabrück, Germany
* Corresponding author: email@example.com
Industrial in-series aluminum castings contain a wide range of microstructural heterogeneities like differences in secondary dendrite arm spacing (SDAS), eutectic silicon and intermetallic precipitates of varying morphologies and diverse-shaped and-sized porosity. Regarding to technical and economic limitations, the complete elimination of them is hard to achieve, which requires conservative design, i.e., increased wall thicknesses to accommodate the failure tolerance. To improve the performance of cast aluminum products concerning safety and fatigue properties, the present work deals with the significance of such structures with respect to the threshold for crack propagation ΔKI,th under pure bending and the fatigue behaviour in the high-and very-high-cycle-fatigue regime (HCF and VHCF). Therefore, two automotive cast alloys taken from engine blocks (AlSi8Cu3) and cylinder heads (AlSi7Cu0.5Mg) and a gravity die cast set (AlSi7Mg0.3), either T6 conditioned or additionally hot isostatic pressed (HIP), were used. For in-series castings, two positions of maximal difference in cooling rate and respective microstructure were extracted. With this set of specimens, the significance of SDAS in interaction with (i) eutectic silicon regions, (ii) intermetallic precipitates in varying occurrence, (iii) the crystallographic orientation, and (iv) the porosity in correlation with the fatigue threshold is shown and compared with first results of fatigue damaging mechanisms in quasi pore-free material.
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (http://creativecommons.org/licenses/by/4.0/).
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