Horizontally Solidified Al–3 wt%Cu–(0.5 wt%Mg) Alloys: Tailoring Thermal Parameters, Microstructure, Microhardness, and Corrosion Behavior

Abstract

In the present experimental investigation, Al–3 wt%Cu and Al–3 wt%Cu–0.5 wt%Mg alloys castings are produced by a horizontal solidification technique with a view to examining the interrelationship among growth rate (GR), cooling rate (CR), secondary dendrite arm spacing (λ2), Vickers microhardness (HV), and corrosion behavior in a 0.5 M NaCl solution. The intermetallic phases of the as-solidified microstructures, that is, θ-Al2Cu, S–Al2CuMg, and ω-Al7Cu2Fe, are subjected to a comprehensive characterization by using calculations provided by computational thermodynamics software, optical microscopy, and scanning electron microscopy/energy-dispersive spectroscopy. Moreover, electrochemical impedance spectroscopy and potentiodynamic polarization tests have been applied to analyze the corrosion performance of samples of both alloys castings. Hall–Petch-type equations are proposed to represent the HV dependence on λ2. It is shown that the addition of Mg to the Al–Cu alloy has led to a considerable increase in HV; however, the Al–Cu binary alloy is shown to have lower corrosion current density (icorr) as well as higher polarization resistance as compared to the corresponding results of the Al–Cu–Mg ternary alloy.