Effects of Dwell Time on the Deformation and Fatigue Behaviour of A356-T7 Cast Aluminium Alloys Used in High Specific Power IC Engine Cylinder Heads.

The continuous drive towards higher specific power and lower displacement engines in recent years place increasingly higher loads on the internal combustion engine materials. This necessitates a more robust collection of reliable material data for computational fatigue life prediction to develop reliable engines and reduce developmental costs. Monotonic tensile testing and cyclic stress and strain-controlled testing of A356-T7 + 0.5 wt.% Cu cast aluminium alloys have been performed. The uniaxial tests were performed on polished test bars extracted from highly loaded areas of cast cylinder heads. The monotonic deformation tests indicate that the material has an elastic-plastic monotonic response with plastic hardening. The strain controlled uniaxial low cycle fatigue tests were run at multiple load levels to capture the cyclic deformation behaviour and the corresponding fatigue lives. The equivalent stress-controlled fatigue tests were performed to study the influence of the loading mode on the cyclic deformation and fatigue lives. The two types of tests exhibit similar fatigue lives and stress-strain responses indicating minimal influence of the mode of loading in fatigue testing of A356 + T7 alloys. The material exhibits a non-linear deformation behaviour with a mixed isotropic and kinematic hardening behaviour that saturates after the initial few cycles. There exists significant scatter in the tested replicas for both monotonic and cyclic loading.