On the impact toughness of Al–Si cast alloys

Abstract

The present study was carried out on two Al–Si alloys viz. B319.2 and A390.1, in order to determine their impact toughness under certain test conditions. The results show that due to the presence of mixed types of silicon in the A390.1 alloy, it is not possible to quantify their sizes. Moreover, due to the difference in the densities of Si and Al, the primary Si particles tend to segregate in certain areas, leading to an inhomogeneous distribution of these particles, and, in turn, a marked deviation in the alloy toughness from one sample to another. The presence of Fe-based intermetallics was shown to have lowered the impact energy values of the B319.2 alloy (with 7% Si) in the as-cast condition to reach those values obtained in the A390.1 alloy (with 17% Si). The B319.2 alloy demonstrated a noticeable response to the applied heat treatment. The A390.1 alloy, however, did not exhibit such a variation in toughness as a function of test condition. This was primarily attributed to the presence of a large number of coarse primary Si.