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

Abstract

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 μm 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.