Microstructure, defects and fatigue behavior of cast AlSi7Mg alloy

The cast AlSi7Mg alloy prepared using different modifier was studied. The main factor influencing fatigue properties were the casting defects. Using metallography and statistical approach, Larger Extreme Value Distribution (LEVD) theory, the structure and the porosity were evaluated. According to the largest defects sizes prediction fatigue tests were performed. Fatigue cracks were initiated on the casting defects present on the specimen free surface or just below the surface identified using SEM. Specimens fatigue life was influenced by the size of the defect in the initiation place and the number of initiation places. The specimens fatigue behaviour corresponded with the assumptions according to the LEVD