Evaluation of Fatigue, Oxidation and Creep Damages in A356.0 Aluminum Alloy under Cyclic Isothermal and Un-isothermal Loadings

In this article, fatigue, oxidation and creep damages in the A356.0 aluminum alloy (including an aluminum-silicon-magnesium alloy, which has been used in diesel internal combustion engines) have been investigated under isothermal and un-isothermal cyclic loadings. In order to calculate different damages, Sehitoglu’s model was utilized, in which the total damage in materials under hightemperature cyclic loadings include the fatigue damage, the oxidation damage and the creep damage. Material constants in this model for the mentioned alloy were calculated by experimental data from isothermal fatigue tests (or low-cycle fatigue tests at constant room temperature and at 250°C) and non-isothermal fatigue tests (or out-of-phase thermo-mechanical fatigue tests) were performed on test specimens. Obtained results showed that the main damage under out-of-phase thermo-mechanical fatigue loadings was the oxidation and under high-temperature low-cycle fatigue loadings was the creep phenomenon. In addition, the model used for the A356.0 aluminum alloy had generally a proper accuracy and in lower strains (higher lifetimes), the error was increased. The standard error for Sehitoglu’s model under thermo-mechanical and low-cycle fatigue tests was 0.006 and 0.005%, respectively and the relative error for the total damage was 21 and 10%, respectively.