The Structure of Electrodeposited Aluminum Alloys from Chloroaluminate Ionic Liquids: Let’s Not Ignore the Temperature

Abstract

Electrodeposited alloys are rarely in thermodynamic equilibrium, and several unique microstructural features such as extended solid solubility, metastable crystalline phases, and metallic glasses are generally observed. Because the excess free energy of the deposit is inversely proportional to the atomic mobility, phase constitution depends strongly on deposition temperature. This paper examines the influence of deposition temperature on the crystal structure of electrodeposited Al-Mn and Al-Ti alloys electrodeposited from AlCl3-NaCl and AlCl3-EMImCl ionic liquids from temperatures ranging from 80 °C to 425 °C. Deposition at low temperature favors the preferential deposition of amorphous and crystalline phases which appear as high temperature variants in the equilibrium phase diagram. These structures generally have high symmetry, and for this reason are relatively easy to nucleate. The room temperature equilibrium phases, which generally have a more complicated structure, can only be obtained at elevated deposition temperatures.