For related shape memory application resources, Design for Disassembly, Eco-Design, Environment and AD Technology guidelines related to this can be downloaded for free at:
Toward a better understanding of Shape Memory Alloys
Since its discovery in the early 1960s, near equiatomic Ni-Ti alloy has attracted a lot of attention due to its unique functional properties (superelasticity, one-way and two-way shape memory) and its excellent mechanical properties (low elastic anisotropy, high resistance to corrosion and abrasion, …). Its crystallographic structure can change from the cubic austenite to the monoclinic martensite through the application of temperature or strain. It is from this reversible phase transformation that the unique functional properties of NiTi originate.
Ni-Ti alloys are mainly produced in the form of thin wires in a cold-worked state, which do not show any specific properties. To achieve the functional properties, a heat treatment, which traditionally can take up to 1 hour in a furnace, is needed. Recently, a non conventional technique called Final Thermo-Mechanical Treatment by Electric Current (FTMT-EC) has been developed, enabling a reduction in the time needed to heat treat a wire down to a few milliseconds.
In this talk, I will present new results related to the influence of this new heat treatment on the evolution of the microstructure and to properties of the wires which have been subjected to this new technique. These results are based on data obtained from experiments performed at the ESRF, on the Material Science Beamline ID11 and the High Resolution Powder Diffraction Beamline ID31.