Combinatorial studies of mechanical properties of Ti–Al thin films using nanoindentation

Abstract

In this paper, we describe an on-going effort to develop a thin film combinatorial method for identifying alloy compositions of potential interest as structural materials. To investigate this idea, compositionally graded Ti–Al thin films have been sputter deposited onto Si substrates, and the mechanical properties of the “library” of compositions are then probed using nanoindentation. This combinatorial method offers the possibility of rapidly varying the compositions and microstructures of alloys and quickly determining the compositions and microstructures of greatest interest for further development as bulk structural alloys. Nanoindentation experiments are used to extract the properties of the film so that the bulk properties of the material may be estimated. A new method for extracting the hardness of films on substrates from nanoindentation experiments has been developed and is applied to the compositionally graded Ti–Al thin films. Together with the nanoindentation data and a compositional analysis, we are able to establish a relationship between the hardness of the film and the composition. We discuss the results of these combinatorial experiments in connection with estimating the properties of bulk materials.