Relationship between Pores Volume (by Density Measurements) and Pores Area (on Fracture Surfaces) of A356 Fatigue Specimens

The mechanical properties of A356 alloy are largely influenced by the solidification microstructure and especially by defects, such as gas pores, shrinkage cavities and oxide films. For this reason, casting simulation software to predict pores volume, in complex castings, were developed. Few data, however, are available about the relationship between the volume of pores and their distribution on zones of the casting where the failure is localized. The aim of this paper was to find a relationship between the pore volume in fatigue specimens (evaluated by density measurement) and the pore area, measured on their fracture surfaces. The preliminary results show that the pore area fraction, on the fatigue fracture surfaces, can be greater than 10 times the mean volume percentage, so that samples with 1% in volume of defects showed a decrease of the cross-sectional area of about 10%.