A new method for characterizing nanocrystalline NiTi wires using a dynamic mechanical analyzer

The deformation processes in nanocrystalline NiTi wires are very different from conventional intermetallic compounds due to their complex twinned martensitic microstructure. To better understand the mechanisms underlying strain accummulation, nanocrystalline NiTi wires with different grain size were tested in the dynamic mechanical analyzer (DMA). We expected that during the martensitic transformation, the wire would change not only static properties, which have been extensively studied experimentally, but also the dynamic properties characterizing, for example, the energy storage capability of the material. In other words, it allows you to identify and measure changes in elastic properties that cannot be tracked during static tests. It will be shown that changes in the dynamic parameters of the material strongly correlate with the processes observed during conventional thermal cycling in a static mode. This connection is still unknown, despite the widespread use of NiTi in technology. The results obtained can serve to provide a deeper understanding of the nature of the processes occurring in NiTi during the martensitic transformation and lead to optimization of the properties of wires used in devices. The proposed testing method opens up new perspectives in SMA research.