Relationships between Material Ductility and Characteristic Size of Porosity Correlated before/after Testing of a Cast Aluminum Alloy

In this paper, an attempt is made to investigate the relationships between the material ductility and the characteristic size of casting porosities correlated by two different sources. The first source is the metallographic analysis on the cross section before testing. The second one is the fractographic analysis on the fracture surface after testing. Three types of cast round bars are manufactured with various levels of porosity. An image processing code is developed within Matlab to quantify the size and number of the porosities. It is found that the three types of aluminum cast components have similar microstructure and the same true stress-strain curve is able to predict well the load-displacement response of the three types of castings. A large variation in the size of the largest pore and the area fraction of pores is observed among the cast components. Three distinct fracture loci are predicted using a combined experimental-numerical approach. The material ductility tends to decrease with the increasing size of the pores based on the correlations of two sources. A linear relationship is used to correlate the ductility with the size and number of this type of pores. The correlated trend between the material ductility and the pore size is similar qualitatively on the specimens before/after testing. It is also shown that the effect of the porosity on the material ductility can be preferably correlated by the area fraction of pores measured before testing and after testing in a linear way, respectively.