Microstructural-based Analysis and Modelling of the Fatigue Behaviour of Cast Al-Si Alloys

Analyse et modélisation du comportement en fatigue des alliages d'aluminium de fonderie

Viet Duc Le (1, 2, 3) , Franck Morel (2) , Daniel Bellett (2) , Etienne Pessard (2) , Nicolas Saintier (3) , Pierre Osmond (1)

1 PSA - PSA Peugeot - Citroën
2 LAMPA - PMD - Laboratoire des Arts et Métiers ParisTech d'Angers - Procédés Matériaux Durabilité
3 I2M - Institut de Mécanique et d'Ingénierie de Bordeaux

This paper describes a microstructural-based high cycle fatigue behaviour model applied to cast Al-Si alloys used in an automobile context. These materials are characterized by the presence of different microstructural heterogeneities at different scales: the aluminium matrix (DAS/SDAS and the precipitation hardening level), inclusions (Si particles and intermetallic) and casting defects (porosity). It is shown that the effects of these factors on the HCF damage mechanisms are important and can depend on the loading mode. A multiaxial fatigue test campaign has been carried out using three cast aluminium alloys, fabricated by different casting processes (gravity die casting and lost foam casting), associated with several heat treatment(T7 and Hot Isostatic Pressing-HIP). The HIP treatment is used to eliminate or minimise the porosity. The first part of the article is dedicated to the experimental characterization of the HCF damage mechanisms. With regard to the effect of the casting defects, a study of natural fatigue crack growth and artificial long crack growth is presented and subsequently used to choose an appropriate fatigue strength criterion to take into account the effect of defects, for different loading modes (tension, torsion and combined tension-torsion). Finally, a flexible modelling framework, providing the possibility of combining any two suitable criteria, which leads to the construction of a multiaxial Kitagawa-Takahashi diagram, is used.

Mots clés: High cycle fatigue; Multiaxial; Cast aluminium alloy; Defect; Modelling; Probabilistic

Domaines: Mécanique des matériaux [physics.class-ph]

Viet Duc Le, Franck Morel, Daniel Bellett, Etienne Pessard, Nicolas Saintier, et al.. Microstructural-based Analysis and Modelling of the Fatigue Behaviour of Cast Al-Si Alloys. 6th International Fatigue Design Conference, Nov 2015, Senlis, France. pp.562-575, ⟨10.1016/j.proeng.2015.12.630⟩. ⟨hal-02486657⟩