Porosities and Fatigue Property of Two A356 Cast Aluminum Alloy

To investigate the fatigue property of A356 cast aluminum alloy, the pore size distribution in two kinds of A356 alloy were statistically tested, and the S-N curves were plotted by conducting four-point bend fatigue test, then the fractography of the fatigue specimens were examined under scan electron microscope (SEM). It was indicated that the fatigue strength of the A356.2 alloy contenting more large pores and rougher crystalline grain was lower than that of A356.1 alloy, though the yield strength of A356.2 alloy was higher. Most of the fatigue cracks initiated from the pores that located on or close to the surface of the specimens, and the fracture of the specimens were induced from the growth of multi-sites initiated fatigue crack.