The development of novel diesel cylinder heads lends to a higher complexity of shape and occurring stresses during lifetime. This significantly increases the demands on strength, elongation and creep properties at elevated temperature es, for Al-Si cast alloys. Due to these requirements, an optimization and further development of existing cast alloys was motivated. Mechanical properties and physical data were investigated for various cylinder head alloys. These were the primary alloys Al-Si7-Mg and Al-Si9-Mg; furthermore, two new versions with 0.5 and 1.0% Cu, based on the primary alloy Al-Si7-Mg and, finally, two secondary alloys, Al-Si10-Mg and Al-Si9-Cu3. The two new copper versions of the Al-Si7-Mg alloy were found to improve tensile strength in the temperature range from 150-200C, significantly, as well as creep properties, in comparison to rite established primary alloys. A minor decrease in elongation has to be taken into account. Important physical properties, such as coefficient of thermal expansion and heat conductivity, were hardly affected by alloying copper to the primary base alloy. The comparison of the new copper versions with the secondary alloys exhibits strength and creep properties on a similar level. High tolerated impurities for the Al-Si9-Cu3 led to significantly lower strain-to-failure values; but, on the other hand, this alloy provides the best strength and creep properties at 250C. The hot tearing tendency, as one important casting property, was investigated for the primary alloys. The new copper versions,were found to have nearly the same hot tearing tendency as the Al-Si7-Mg alloy. Further investigations are needed to Sind the optimum content of copper or for possible further hardening elements. The addition of 0.5% Cu to the Al-Si7-Mg has nearly the same effect on mechanical properties as achieved by 1.0% copper.
