PSI - Issue 23

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Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000 – 000 Structural Integrity Procedia 00 (2019) 000 – 000

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ScienceDirect

Procedia Structural Integrity 23 (2019) 511–516

© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the ICMSMF organizers © 201 9 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the IC MSMF organizers. Abstract Al-Si c st alloys are accompanied by differe t defects and microstructural hete ogeneities like porosity, var ing secondary d drite arm spacings (SDAS) and mu tiple appearances of the ute tic. These issues are well know but technically diffic lt to prevent for the industry. To improve the lig t weight performanc f cas aluminum alloys th present work de ls with influen es on crack initiation and pr pagation mechanisms of uch heterogeneities in the high cycl -fatigue (HCF very-hi h-cycle-fatigue (VHCF) r gime for the two hypo-eutecti cast aluminum alloys AlSi8Cu3 (in-series sand c stings) and AlSi7Mg0.3 (lab ra ory gravity di castings). Fu thermo e, the ccurrence of facet-regions and the r role in early and lat s ate of fatigue damage evol t on s discussed by showing r sults from modified Kitagawa-Ta ahashi a alysis and ex-situ computed tomography investigation during int rmi t d HCF exp riments. In the early HCF regime crack ini ia ion starts at multiple pores. Due to coal scence f these defects, hear-stress-contr lled crack p opagation along slip bands leads to the occurrence of facets. In the VHCF reg me, porosity provides strong scattering of the n mber of cycles to failure. A reduct on i SDAS increases h fatigue str ngth signific tly. However, in absence of porosity fa igue rack initiation and propagation is controll d by shear stres es on facet-like slip-planes. Additionally, the barrier role against dislocation movement of eutectic regions can be shown by means of these specimens. © 201 9 The Authors. Published by Elsevier B.V. This is an ope access article under h CC BY-NC-ND lic nse (http://creativecommon org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the IC MSMF organizers. 9th International Conference on Materials Structure and Micromechanics of Fracture Microstructural influences on the fatigue crack initiation and propagation mechanisms in hypo-eutectic Al-Si cast alloys Sascha Gerbe a *, Jochen Tenkamp b , Steffen Scherbring c , Kevin Bleicher b , Ulrich Krupp a , Wilhelm Michels c , Frank Walther b a Steel Institute, RWTH Aachen University, Intzestr. 1, Aachen, 52072, Germany b Department of Materials Test Engineering, TU Dortmund University, Baroper Str. 303, Dortmund, 44227, Germany c Institute of Materials Design and Structural Integrity, University of Applied Sciences Osnabrück, Albrechtstr. 30, Osnabrück, 49076, Germany Abstract Al-Si cast alloys are accompanied by different defects and microstructural heterogeneities like porosity, varying secondary dendrite arm spacings (SDAS) and multiple appearances of the eutectic. These issues are well known but technically difficult to prevent for the industry. To improve the light weight performance of cast aluminum alloys the present work deals with influences on crack initiation and propagation mechanisms of such heterogeneities in the high-cycle-fatigue (HCF) and very-high-cycle-fatigue (VHCF) regime for the two hypo-eutectic cast aluminum alloys AlSi8Cu3 (in-series sand castings) and AlSi7Mg0.3 (laboratory gravity die castings). Furthermore, the occurrence of facet-regions and their role in early and late state of fatigue damage evolution is discussed by showing results from modified Kitagawa-Takahashi analysis and ex-situ computed tomography investigation during intermitted HCF experiments. In the early HCF regime crack initiation starts at multiple pores. Due to coalescence of these defects, shear-stress-controlled crack propagation along slip bands leads to the occurrence of facets. In the VHCF regime, porosity provides strong scattering of the number of cycles to failure. A reduction in SDAS increases the fatigue strength significantly. However, in absence of porosity fatigue crack initiation and propagation is controlled by shear stresses on facet-like slip-planes. Additionally, the barrier role against dislocation movement of eutectic regions can be shown by means of these specimens. 9th International Conference on Materials Structure and Micromechanics of Fracture Microstructural influences on the fatigue crack initiation and propagation mechanisms in hypo-eutectic Al-Si cast alloys Sascha Gerbe a *, Jochen Tenkamp b , Steffen Scherbring c , Kevin Bleicher b , Ulrich Krupp a , Wilhelm Michels c , Frank Walther b a Stee Insti ute, RWTH Aachen University, Intze tr. 1, Aachen, 52072 Ge many b D partment of Materials Test E gineering, TU Dortmund University, Baroper Str. 303, Dor mund, 44227, Germany c Institute of Materials Design and Structural Integrity, University of Applied Sciences Osnabrück, Albrechtstr. 30, Osnabrück, 49076, Germany

Keywords: cast aluminum; fatigue; HCF; VHCF; porosity; SDAS; microstructural barrier; crack propagation Keywords: cast aluminum; fatigue; HCF; VHCF; porosity; SDAS; microstructural barrier; crack propagation

* Corresponding author. Tel.: +49 241 80 95800; fax: +49 241 80 92253. E-mail address: sascha.gerbe@iehk.rwth-aachen.de * Correspon ing author. T l.: +49 241 80 95800; fax: +49 241 80 92253. E-mail address: sascha.gerbe@iehk.rwth-aachen.de

2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the IC MSMF organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an ope acces article under CC BY-NC-ND lic nse (http://creativecommon org/licenses/by-nc-nd/4.0/)

Peer-review under responsibility of the scientific committee of the IC MSMF organizers.

2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the ICMSMF organizers 10.1016/j.prostr.2020.01.137