Effect of growth velocities on microstructure and mechanical properties of eutectic Al–Si–Mg–Ni–(Fe) alloy

In this study, the effect of microstructure on the hardness and tensile-strength properties of Al–Si–Ni–Mg quaternary eutectic alloy system at different growth velocities were investigated. The composition of Al–Si–Ni–Mg quaternary eutectic alloy system was chosen to be Al–13 wt%Si–3.5 wt%Mg–2 wt%Ni. The chemical composition of the alloys was determined by using XRF (x-ray fluorescence). Al–Si–Ni–Mg quaternary eutectic alloy system was directionally solidified at different growth velocities, 8.3 to 166.6 μm.s−1 by using a Bridgman-type furnace. The eutectic temperature of the quantitative alloy is 552.13 °C measured by DTA (Differential Thermal Analysis). The quantitative chemical composition analyzes of the phases were carried out by using energy dispersive spectroscopy (EDS), x-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) images and according to the EDX and XRD results and SEM images, Mg2Si, Al3Ni, Si and Al9(Ni,Fe)Mg3Si5 phases were identified with in Al matrix phase. The lamellar spacing (λ) for Mg2Si, Al3Ni, Si, and Al9(Ni,Fe)Mg3Si5 phases were measured from transverse sections of the samples. The dependencies of lamellar spacing (λ), microhardness and tensile-strength on growth rates were obtained as: respectively for the Al–Si–Mg–Ni eutectic alloy.