Composition-Structure-Function Diagrams of Ti-Ni-Au Thin Film Shape Memory Alloys

摘要

Ti-Ni-Au thin film materials libraries were prepared from multilayer precursors by combinatorial sputtering. The materials libraries were annealed at 500, 600, and 700 degrees C for 1 h and then characterized by high-throughput methods to investigate the relations between composition, structure and functional properties. The identified relations were visualized in functional phase diagrams. The goal is to identify composition regions that are suitable as high temperature shape memory alloys. Phase transforming compositions were identified by electrical resistance measured during thermal cycles in the range of -20 and 250 degrees C. Three phase transformation paths were confirmed: (1) B2-R, (2) B2-R-B19', and (3) B2-B19. For the materials library annealed at 500 degrees C only the B2-R transformation was observed. For the materials libraries annealed at 600 and 700 degrees C, all transformation paths were observed. High transformation temperatures (M-s approximate to 100 degrees C) were only obtained by annealing at 600 or 700 degrees C, and with compositions of Ti approximate to 50 at. % and Au > 20 at. %. This is the composition range that undergoes B2-B19 transformation. The phase transformation behaviors were explained according to the compositional and annealing temperature dependence of phase/structure formation, as revealed by X-ray diffraction analysis of the materials libraries.