C © Owned by the authors, published by EDP Sciences, 2014 Improvement of mechanical behaviour of cylinder head alloys

Cylinder heads of combustion engines are exposed to complex loading conditions in service. With respect to the efforts made in terms of carbon reduction and fuel consumption these parts were continuously optimized in numerous research projects during the last two decades [1–6]. Additional efficiency increase is directly related to improved high temperature material performance. Besides the development of new lightweight alloys detailed knowledge about the specific mechanical behaviour at elevated temperatures is essential for advances in design and lifetimes under service conditions. In particular, the interaction of complex thermal and mechanical forces under service loading is one of the major factors affecting the lifetime [7]. In this paper the thermo-mechanical fatigue (TMF) behaviour of three cast AlSiMg alloys with small modifications of the chemical composition is investigated under out-of-phase uni-axial loading according to [8]. In detail the Si was modified, while the Magnesium content was kept nearly constant. The alloys were heat treated according to T6 representing maximum precipitation hardening. The results are compared to TMF data of the alloy AlSi6Cu4 representing a standard as this alloy is used in service. The heat treated state was also T6. TMF tests (R = 1) were performed on solid cylindrical specimens in air in a temperature range between 200–400 ◦C. Strain amplitudes from 0.2 % to 0.7 % were applied