|About this Abstract
||2018 TMS Annual Meeting & Exhibition
||Frontiers in Advanced Functional Thin Films and Nanostructured Materials
||M-19: Synthesis and Mechanical Behavior of a Freestanding, Nanocrystalline NiTi Film under Cyclic Tensile Deformation
||Paul Rasmussen, Jagannathan Rajagopalan, Rohit Sarkar
|On-Site Speaker (Planned)
Controlling the micro/nanostructure of thin films would enable us to explicitly tailor their mechanical behavior. Here, we describe a new process to synthesize thin films with precise microstructural control via systematic, in-situ seeding of nanocrystals, and subsequent crystallization of amorphous precursor films. Using this process, we synthesized an austenitic NiTi film with a mean grain size of around 100 nm. We then co-fabricated freestanding samples of the film with MEMS testing stages and performed cyclic tensile load-unload experiments. The film showed a high phase transformation stress (> 700 MPa) during the first cycle that increased even further during subsequent cycles. More interestingly, the film showed a continuous decrease in stress-strain slope during unloading rather than the pseudo-elastic behavior typically observed in microcrystalline NiTi. Preliminary in-situ TEM straining studies suggest that this unusual loading behavior is caused by a combination of reverse phase transformation and reverse plasticity.
||Planned: Supplemental Proceedings volume