Effects of Alloying Elements Additions on Ambient Temperature Performance of Al–Si–Cu–Mg Base Alloys

Abstract

The present study was carried out to investigate the effects of Ni, Mn, Zr, and Sc additions, individually or in combination with other additives, on the microstructure and tensile properties of 354 casting alloy (Al—9wt%Si—1.8wt%Cu—0.5wt%Mg) at room temperature. Tensile tests were carried out in the as-cast, solution heat-treated, and aged conditions using different aging temperatures and times. Six alloys were prepared using the 354 alloy, comprising a) the base 354 alloy (G1) and five other alloys (G6 to G10) containing Ni, Mn, Sc, Zr, added individually or in combination, and comprising one experimental alloy (G7) containing no copper. Among the alloys containing transition element additions (G6 through G10), the highest tensile and yield strength values are obtained with alloy G7 (2wt% Ni and 0.25wt% Zr but no Cu) in the as-cast and solution heat-treated conditions; alloys G8 and G10 also display a significant increase in tensile strength and ductility in the as-cast and solution heat-treated conditions. Solution heat treatment significantly improves strength and quality of these alloys even if they contain higher Fe and Mg levels compared to the base alloy. Holding the tensile samples of T6-treated G1 alloy resulted in a marked increase in the density of precipitated phase in the form of fine spherical particles. Increasing the holding time prior to deformation to 100 h resulted in the change in the morphology of the Al2Cu precipitates into thin platelets distributed in two perpendicular directions.