Hard and corrosion-resistant aluminum alloys with extended nickel solid solubility through electrodeposition in imidazolium ionic liquids

Coarse intermetallic compounds present in aluminum (Al) alloys significantly increase their susceptibility to localized corrosion, creating a trade-off between strength and corrosion resistance. In this study, Al−Ni alloys with a homogeneous microstructure were obtained through electrodeposition using imidazolium ionic liquids (ILs). Theoretical calculations and spectral analyses revealed that Ni(II) existed as an octahedral coordination complex, [Ni(Al₂Cl₇)₄]^2 −, in Lewis-acidic ILs. This complex interacted with the Al₂Cl₇⁻ species, facilitating the co-deposition of Al and Ni into supersaturated solid solutions Al(Ni). These deposits exhibited superior hardness compared to as-cast counterparts, reaching 3.9 GPa for Al(Ni) with 4.1 at% Ni, while also demonstrating enhanced corrosion resistance over pure Al. This simultaneous improvement in hardness and corrosion resistance is attributed to the homogeneous structure and extended Ni solubility. Consequently, the electrodeposition of Al(Ni) supersaturated solid solutions presents a promising approach to optimizing strength and corrosion resistance.