Maintaining strength in supersaturated copper–chromium thin films annealed at 0.5 of the melting temperature of Cu

The thermal stability of evaporated copper–chromium alloy films was studied by correlating hardness trends from nanoindentation to nanostructural–compositional changes from transmission electron microscopy. In particular, the hardness evolution with ageing time at ambient and elevated temperatures of two compositions, dilute (Cu96Cr4) and chromium-rich (Cu67Cr33) solutions, was studied. Due to the negligible mutual miscibility of copper and chromium, the chosen solid solutions are trapped in metastable states as supersaturated solid solutions with face-centred cubic and body-centred cubic phases. Nano-mechanical probing of the nanostructural evolution as a function of temperature provided interesting insights into the phase separation of these systems.