Enhanced superelasticity and two-way shape memory properties of bamboo-grained Au7Cu5Al4 microwires

A bamboo-like grain structure was obtained in melt-extraction Au7Cu5Al4 microwires via cyclic heat treatment. The superelasticity and two-way shape memory properties were investigated by performing uniaxial cyclic tensile tests and mechanically constrained thermal cycling, respectively. The superelasticity of bamboo-grained microwires was improved significantly duo to a reduction in the constraints caused by triple junctions. A recoverable strain of ∼3% was achieved over a wide temperature range of 358–423 K for the bamboo-grained microwire, which exhibited excellent cyclic stability under a stress of up to 470 MPa. The two-way shape memory properties were determined by conducting load-biased thermal cycling tests, and a recoverable strain of 1.2% with a maximum work output of 1.2 J cm−3 was achieved under a stress of 100 MPa. The results indicate that the Au–Cu–Al shape memory alloy is a potential candidate for small-sized actuators operating in harsh environments. [Display omitted] •A bamboo-grained Au–Cu–Al microwire was obtained via cyclic heat treatment.•A recoverable strain of ∼3% was achieved over a wide temperature range of 358–423 K.•The microwire shows an excellent cyclic stability under the stress of up to 470 MPa.•Two-way shape memory effects of Au–Cu–Al SMAs were determined for the first time.