On the role of process variables in the friction stir processing of cast aluminum A319 alloy

The surfaces of cast A319 alloy plates of nominal composition (wt.%): Al – 5.2 Si – 2.51 Cu were subjected to single stir Friction Stir Processing (FSP) with a view to decreasing the grain size and porosity level and improving the mechanical properties. Three traverse feed rates and five tool rotational speeds were employed. For certain combinations of the variables, the processed alloy displayed an increase in value of around 50% in tensile strength and 20% in microhardness compared with those of the as-cast alloy. The ductility of the processed alloy had increased by a factor which ranged from 1.5 to 5.Optical and scanning electron microscopy revealed that FSP reduces the size of the second phase particles, which contributes to the improvements in mechanical properties.