Combinatorial fabrication and high-throughput characterization of a Ti–Ni–Cu shape memory thin film composition spread

Abstract The phase transformation properties of Ti–Ni–Cu shape memory thin films prepared in the form of a continuous composition spread were investigated. The thin film materials library was fabricated from elemental targets using an ultra-high vacuum combinatorial magnetron sputter-deposition system. Alternating wedge-type layers of Ti, Ni, and Cu were deposited on a thermally oxidized Si wafer and subsequently annealed at 500 °C for 1 h in situ . Automated temperature-dependent resistance measurements ( R ( T )), energy dispersive X-ray analysis and X-ray diffraction measurements revealed the compositional region in the ternary phase diagram where thermoelastic transformations occur. The transformation temperatures and the thermal hysteresis were determined from R ( T ) measurements. Within the composition spread an extended transformation region was found. For Ni-rich compositions, a two-stage B2 → R → B19′ phase transformation was observed. Among others, compositions of Ti 51 Ni 49− x Cu x (at.%) show a single-stage transformation for a Cu-content 14 at.% (B2 → B19). In the intermediate composition range two-stage transformations (B2 → B19 → B19′) were found. The dependency of the thermal hysteresis on the Cu-content as described in the literature was confirmed.

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