Papers by Keyword: Shrinkage Pore

Abstract: The fatigue strength of cast Al-Si alloys is strongly sensitive to the presence of casting defects. Extensive rotating bending fatigue testing of cast AlSi7Mg alloy at room temperature and 50 Hz is reported showing that shrinkage pores are the critical casting defect. The porosity of selected fatigue specimens extracted from castings is characterized with metallography using different pore sizing criteria. Data are fitted to EVS distributions and used for critical size prediction. Fatigue fracture surfaces are inspected in the SEM and the critical pores originating the fatigue cracks identified and measured according to criteria used in the metallographic inspection.

Abstract: The sand casting process usually generates porosity that is highly detrimental especially to the fatigue behavior of Al-Si alloys. Since pores favor early fatigue crack initiation, the total fatigue life is crack-propagation-dominated and, for a given stress level, strongly depends on the initiating pore size. Here long life fatigue strengths were estimated using specimens extracted from different AlSi7Mg castings. Detailed metallographic characterization of specimen sections was carried out to determine pore size distributions and correlate it to test results. Murakami’s experimental procedure for applying the largest extreme value statistics to small defect characterization is applied and discussed.