The electrodeposition of non-equilibrium Al-W alloys was investigated in the Lewis acidic 66.7-33.3 percent mole fraction aluminum chloride-1-ethyl-3-methylimidazoliurn chloride (AlCl3-[EtMeIm]Cl) room-temperature ionic liquid (IL). The W(III) compound, K-3[W2Cl9], served as the reservoir for W. Both controlled potential and controlled current techniques were employed. Depending on the electrodeposition conditions, it was possible to prepare Al-W alloys with a W content approaching 96 percent atomic fraction (a/o). However, as the W content of these alloys increased above 30 a/o, the deposits became powdery and friable and were difficult to characterize. XRD analysis of deposits containing similar to 16 a/o W revealed a broad reflection consistent with the amorphous phase that typically appears at alloy concentrations that exceed the limit of the supersaturated solid solution. This phase is not readily apparent in X-ray diffraction patterns until the W content reaches about 9 a/o. As expected, the lattice parameter for the fcc Al phase decreased as the W content of the alloy increased, reaching a maximum contraction of about 0.2%, consistent with a W content of about 5 a/o. This suggests that the amorphous phase may be present in deposits containing a little as 5 a/o W. Alloys containing similar to 3 a/o W were dense and compact and displayed a chloride pitting potential of +0.3 V versus unalloyed Al. Heat treatment was explored as a method to address the powdery morphology of those deposits with a high W content, but XRD analysis indicated that this approach leads to the precipitation of at least one new phase (Al5W) and a decrease in the chloride pitting potential. (C) 2014 The Electrochemical Society. All rights reserved.