Isothermal fatigue damage mechanisms at ambient and elevated temperature of a cast Al-Si-Cu aluminium alloy

•Cracks initiate on casting defects at low and high temperature.•Eutectic regions play a larger role on the crack propagation path as temperature increases.•Defects interact and influence the fatigue crack path.•Real size and location of defects has to be considered in order to assess the defect cri...

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Bibliographic Details
Published in:International journal of fatigue 2019-04, Vol.121, p.112-123
Main Authors: Wilson, Pablo, Saintier, Nicolas, Palin-Luc, Thierry, Bergamo, Sebastien
Format: Article
Language:English
Subjects:
Aluminum alloys
Aluminum base alloys
Automobile industry
Automotive engineering
Automotive parts
Castability
Casting defects
Copper
Crack initiation
Crack propagation
Cylinder heads
Engine components
Fatigue failure
Fatigue life
Fracture mechanics
High temperature
High temperature testing
Low cycle fatigue
Materials fatigue
Mechanical properties
Silicon
Surface cracks
Temperature
Thermal conductivity
Tomography
Weight reduction
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Summary:•Cracks initiate on casting defects at low and high temperature.•Eutectic regions play a larger role on the crack propagation path as temperature increases.•Defects interact and influence the fatigue crack path.•Real size and location of defects has to be considered in order to assess the defect criticity.•LCF life and crack growth can be adressed with a crack-like defect approach effectively predicted. Cast aluminium alloys have a key position as structural materials for the automotive industry combining good mechanical performance, excellent castability and thermal conductivity, making them a suitable choice for engine parts such as cylinder heads. In this paper, the low-cycle fatigue behaviour of a cast aluminium alloys is investigated at ambient and elevated temperatures by the use of in situ optical surface crack monitoring, secondary electron microscopy and X-ray tomography which are combined to study the fatigue mechanisms. The observations highlight the effect of defect distribution and temperature on the crack propagation path and in particular the change of the role of eutectic regions as the temperature increases. In addition, based on the defects population analyses by tomography, a fatigue crack initiation model is proposed to consider both temperature and defect effects on the total low-cycle fatigue life and fatigue crack growth rates.
ISSN:0142-1123
1879-3452
DOI:10.1016/j.ijfatigue.2018.11.016