Lifetime of cast AlSi6Cu4 under superimposed thermal–mechanical fatigue and high-cycle fatigue loading

Out-of-phase thermal–mechanical fatigue (TMF) tests with superimposed high-cycle fatigue (HCF) loading were performed at the cylinder-head alloy AlSi6Cu4. For continuously superimposed HCF loading during TMF cycles with maximum temperatures of 250 and 300 °C a threshold of the amplitude of the superimposed HCF loading exists below which the number of TMF cycles to failure is not significantly affected. Above this threshold the TMF life shows a strong decrease with increasing HCF loading. This characteristic lifetime behaviour is also found in the case that HCF loading is only superimposed while tensile stresses are induced in the specimen during the TMF cycle. However, in the case that the HCF loading is superimposed only during the compressive phase of the TMF cycle, the number of TMF cycles to failure is not significantly affected.