Effect of high intensity ultrasonic treatment on the microstructure, corrosion and mechanical behaviour of ac7a aluminum alloy

Abstract

Ultrasonic treatment is one of the most efficient and cost effective processes that are developing in today's technology. It improves mechanical properties, corrosion resistance and homogeneity of the microstructure. In this study, the effect of casting conditions and ultrasonic treatment on the microstructure, hardness and corrosion behaviour of the Al-4.5%Mg alloy was investigated. Alloy ingots were melted in resistance furnace at 750C, and then cast into metallic molds. Pouring temperatures were 750C (superheated) and 639C (liquidus temperature). One sample was poured at 655C and left to solidify in ultrasonic field down to 615C within 2-3 minutes. The microstructure showed a completely coarse dendritic morphology for casting at 750C, and less dendritic morphology with finer grain size when cast at 639C. The finest and most globular aluminum grains and intermetallic particles were obtained by ultrasonic treatment during solidification. Higher hardness values and corrosion resistance were recorded for ultrasonic treated sample in comparison to cast one.