Ultramicrohardness of aluminum and aluminum alloy thin films

The ultramicrohardness (UMH) of vapor-deposited aluminum and aluminum alloy thin films was determined at room temperature by indentation experiments at small indenter forces. For pure aluminum films both the dependence of the measured hardness upon film thickness and the hardness-microstructure relationship are described. The increase in UMH of aluminum by alloying was studied for alloy films prepared by simultaneous vapor deposition of aluminum with the metals silver, copper, titanium or vanadium. The hardness of the pure aluminum films hardly changes upon annealing. The as-deposited aluminum alloy films are single-phase alloys, which are highly supersaturated. Consequently, their hardness values are rather high. Alloy softening was observed after an anneal treatment at relatively high temperature. The importance of the various hardening mechanisms will be discussed.