Modification Effect of Nickle on Tensile Properties and Microstructural ‎Characterization of Al-12%Si-1%Mg-1%Cu alloy‏ ‏

Al–Si alloys are widely used in automotive components, especially with eutectic composition, for cylinder heads, pistons and valve lifters. In the current study, the effect of different concentration of nickel has been investigated on microstructural evolution and tensile strength properties of Al-12%Si-1%Mg-1%Cu-X%Ni alloys. The microstructural assessment of alloys was carried out by an optical (OM) and scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS) analysis. The tensile testing method was performed for both modified and unmodified specimens. The obtained result indicated that the Ni can effectively refine eutectic silicon particles. Depending on the chemical composition of the alloy specimens, different containing phases such as Τ-Al9FeNi, δ-Al3CuNi, γ-Al7Cu4Ni, Q-Al5Cu2Mg8Si6, α-Al15(MnFe)3Si2 and ε-Al3Ni intermetallic in interdendritic regions have been detected. Furthermore, with the increasing of nickel concentration, Ni-containing intermetallics translate from Al3Ni to Al7Cu4Ni or Al3CuNi and their morphologies change from short and long strip-like to chines-script or reticular-shape. Moreover, the results showed that the mechanical performance has been related to the microstructural features. The ultimate tensile strength (UTS) at room temperature increases from 157 MPa to 220 MPa and then decrease to 195 MPa.