Defect-correlated fatigue assessment of A356-T6 aluminum cast alloy using computed tomography based Kitagawa-Takahashi diagrams

•Influence of porosity characteristics on mechanical behavior of A356-T6.•Shrinkage and gas porosity was separated using micro-computed tomography.•Fatigue behavior and fatigue crack propagation behavior of A356-T6.•Fatigue limit was correlated with porosity using Kitagawa-Takahashi diagrams.•S-N cu...

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Bibliographic Details
Published in:International journal of fatigue 2018-03, Vol.108, p.25-34
Main Authors: Tenkamp, Jochen, Koch, Alexander, Knorre, Stephan, Krupp, Ulrich, Michels, Wilhelm, Walther, Frank
Format: Article
Language:English
Subjects:
Aluminum alloys
Aluminum base alloys
Aluminum cast alloy
Casting alloys
Computation
Computed tomography
Computed tomography (CT)
Crack propagation
Deformation
Dendritic structure
Fatigue crack propagation
Fatigue failure
Fatigue life
Fatigue limit
Fatigue tests
Fracture mechanics
High cycle fatigue
High cycle fatigue (HCF)
Kitagawa-Takahashi diagram
Materials fatigue
Microstructure
Morphology
Porosity
S N diagrams
Strength to weight ratio
Tomography
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Summary:•Influence of porosity characteristics on mechanical behavior of A356-T6.•Shrinkage and gas porosity was separated using micro-computed tomography.•Fatigue behavior and fatigue crack propagation behavior of A356-T6.•Fatigue limit was correlated with porosity using Kitagawa-Takahashi diagrams.•S-N curve was evaluated using Paris law and characteristic initial pore size. Modern aluminum cast alloys are promising candidates for highly loaded lightweight components due to their good strength-to-weight ratio. To enable a safe design of aluminum cast components, the microstructure characteristics, e.g. porosity, secondary dendrite arm spacing and Si eutectic morphology, have to be taken into account. This study deals with the influence of different porosity characteristics on the fatigue behavior of A356-T6 aluminum cast alloy. For this purpose, cyclic deformation tests have been carried out to study fatigue damage and fatigue crack growth in the high cycle fatigue (HCF) regime up to 107 cycles. The porosity of each batch was quantified using micro-computed tomography. Results show that large porosity dominates the HCF fatigue behavior. The relationship between porosity characteristics and the fatigue limit as well as S-N curve was assessed by Kitagawa-Takahashi diagrams and a fracture mechanic approach.
ISSN:0142-1123
1879-3452
DOI:10.1016/j.ijfatigue.2017.11.003