Ti–50.8 at.% Ni wire with variable mechanical properties created by spatial electrical resistance over-ageing

This work attempts to develop superelastic TiNi wires with spatially varied shape memory characteristics along their length. A short section of the wire was over-aged by electrical resistance heating, which resulted in the deterioration of its superelasticity, whilst the reminder of the wire length remained superelastic. The tensile stress–strain behaviour of such treated wires is characteristic of two discrete stress plateaus during the stress-induced martensite transformation, corresponding to the original and over-aged sections.

Deformation behaviour of Ti–50.8 at.%Ni wires at 300 K after local over-ageing by electrical heating for different periods of time. The wires exhibit two stress plateaus during the stress-induced martensitic transformation.Figure optionsDownload as PowerPoint slideHighlights
► Local electrical heating suppresses pseudoelasticity of NiTi locally by over-ageing.
► Locally over-aged NiTi wires exhibit two distinctive stress plateaus.
► Locally over-aged NiTi wires exhibit a sequential Lüders band nucleation-propagation behaviour.