Influence of Modifications on Fatigue Strength of AlSi17Cu5Mg(Fe) Alloy Used for Pistons for Internal Combustion Engines

Technological progress in construction of automotive vehicles, particularly in construction of engines, enforces simultaneous changes in foundry properties of aluminum alloys used in automotive industry. Until recently, abrasion resistance was the main usability criterion of a material used for pistons for internal combustion engines. At present however, because of the complexity of the process of the fuel mixture combustion, more restrictive standards of limited hydrocarbon emission, and the pursuit of reduction of the vehicle’s mass, fatigue strength of silumins enjoys a continuously increasing interest. The paper presents results of a computer simulation using the finite element method (FEM) and a real fatigue test of AlSi17Cu5Mg(0.5Fe) (A390.0) alloy with unilateral variable bending. The tests aimed to simulate a deflection of a combustion engine piston in a cylinder barrel were carried out in two variants: for a non-modified alloy and an alloy modified with CuP10 master alloy. Based on the distribution of stresses according to the Huber-Mises-Hencky theory (for a given range of the deflection from 0.1 to 0.3 mm), Wöhler curve was determined for the studied alloy. Based on on microstructural investigations, cracks of primary Si crystals were found, caused by fatigue changes resulting from unilateral pulsating vibrations.