Effect of Ni addition on the microstructure, conductivities and mechanical properties of as-cast Al-Fe alloys

Abstract

In this study, the microstructure, conductivity and mechanical properties of as-casted Al-1Fe-xNi (x= 0, 1, 4, 6 and 10, wt%) alloys were systematically investigated. The results exhibited the Al-1Fe-xNi alloys mainly consist of α-Al, Al3Fe, Al3Ni, and Al9FeNi phase. With the increase of Ni addition, the size of α-Al grain decreases and the dimension of Al9FeNi phase increased. The hardness of the as-cast alloys raises with increasing Ni content, whereas the elongation and electrical conductivity decreases and the ultimate tensile strength (UTS) first increases and then decreases dramatically. The Al-1Fe-6Ni alloy exhibited the highest Q-value, which was approximately 11.27% higher than that of the Ni-free alloys. This mechanism of mechanical properties change occurs mainly due to slightly Ni effectively refines the α-Al phase, and the excessive Ni content leads to formation of coarse needle-like or lath-like Al9FeNi phase. Additionally, the grain refinement and precipitation of the second phase upon Ni addition impede electron movement, leading to a decrease in the electrical conductivity of the alloy. The corresponding ductile fracture morphologies of Al-1Fe-xNi alloys are also analyzed. These high-strength Al-1Fe-xNi alloys could be helpful for developing novel Al-Fe alloys with a high strength and ductility.