Evaluation of the hardness and Young's modulus of electrodeposited Al–W alloy films by nano-indentation

Al–W alloy films with various W contents up to ~ 12 at.% were prepared by electrodeposition using 1-ethyl-3-methylimidazolium chloride (EMIC)–AlCl₃ ionic liquids with different concentrations of W precursor, W₆Cl₁₂. The hardness (H) and Young's modulus (E) of the films were examined by nano-indentation. The films were composed of a single-phase fcc Al super-saturated solid solution, an amorphous phase, or both, depending on the W content and the deposition conditions. The H value increased with increasing W content up to 9.8 at.% and then decreased slightly with further increases in the W content up to 12.4 at.%. A similar trend was observed in the E value with increasing W content, but the decrease in E value at 12.4 at.% W was more significant than that in H value. The changes in the H and E values are discussed from the viewpoints of the grain size and the constituent phases. The 9.8–12.4 at.% W films, which had relatively high H values and H/E ratios, are expected to have a higher resistance to mechanical damage than Al films.