Thin Film Martensites

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9321185 Wuttig This research project examines martensitic transformation in thin films, concentrating on the transformation of austenite on a substrate. This study emphasizes the elastic and anelastic properties of thin film austenite/martensite/substrate composites and use the anelastic properties to characterize the metallurgical changes in the composite as well as the internal stresses. This approach has the major advantage that the structural and microstructural changes, the adhesion and stresses can be monitored and their effect on the transformation investigated, all in-situ and simultaneously. The goal is to learn the effects of substrate constraint and film thickness, and the state of crystallinity and microstructure of the "austenite" on the transformation. In view of their potential practical importance, alloys from the four major shape memory alloy (SMA) families, nickel/titanium-based, copper- based, iron/manganese-based, and iron/platinum/palladium-based, as well as hybrids thereof, are investigated. Characterization techniques include X-ray diffraction, scanning and transmission electron microscopy, and Rutherford back scattering. %%% Emphasized are thermoelastic martensites. The substrates include silicon with different buffer layers because of the potential for micro-mechanical device integration as well as silicon-carbide which is fast becoming one of the more important micro-mechanical materials. ***