On the microstructure and superelastic evolution of laser annealed thin NiTinol wires

Shape setting is a crucial step of the production route of shape memory alloys (SMAs) elements for fixing their functional properties. For thin SMA wires, this peculiar setting can be performed by a laser beam scanning the wire length. In the present work the correlation among the functional properties, such as stress-strain curves, the microstructural properties and the laser power was studied on 100 ?m pseudoelastic NiTi wire. A comparison between the performances of the laser treated and the commercial wires was discussed. It can be stated that the wire responses can be modulated as a function of the laser power; the optimal laser condition can induce functional properties at least comparable to the ones of the wire conventionally treated in a furnace. Laser induced superelasticity was obtained at room temperature and the corresponding microstructure suggests a texture effect associated with the directional and fast heating induced by the laser beam scan. A favorable condition for extended stress induced plateau lengths, compared to the one of the commercially available furnace treated wires, was induced by the laser scan.