Microstructure of TiNi shape memory alloy films made of sputter-deposited Ni/Ti multilayers

Abstract

Phase depth profile in TiNi shape memory alloy films is studied by the combinati on of grazing-incidence X-ray diffraction and X-ray reflectivity measurement. Th e film is made from sputter-deposited Ni/Ti multilayers. At room temperature, bo th the phase depth profile and element depth profile are not uniform, and both h ave multilayer structure. There is a three-phase mixture region consisting of Ti 3Ni4 precipitates, martensite and a little of austenite ne ar the free surface. A uniform martensite phase is formed near the substrate. Di ffusion and reaction take place between film and substrate. The simulation resul t of X-ray reflectivity shows that the results of film microstructure analysis a re reasonable. It is the kinetic factors that mainly cause the ununiformity of p hase depth profile in the film.