Electrical pulse shape setting of thin Ni49Ti51 wires for shape memory actuators

The effect of non-conventional electrical pulse treatment on microstructure and shape memory response of Ni49Ti51 wires was studied. High-power rapid current square pulses were applied to cold-drawn wires of 25 ?m diameter. The TEM microstructures showed equiaxial recrystallization, with average grain size in the 100 nm range, after a double current pulse lasting 10 ms. Rapid current pulse treatment in Ti-rich NiTi induces shape memory effect with reduced thermal hysteresis and high recovery strain values. This novel treatment might replace conventional pre-device shape setting/training of the wire with a post-device shape setting with promising industrial advantages. © 2014 ASM International.