Fabrication and characterization of Cu–Zn–Sn shape memory alloys via an electrodeposition–annealing route

Cu–Zn–Sn shape memory alloys (SMAs) with an average composition of 56.0at%, 36.1at%, and 7.9at% for Cu, Zn, and Sn, respectively, were successfully fabricated via an electrodeposition–annealing route. The produced SMAs were assessed for shape memory response in terms of percent displacement (martensite phase recovery) by subjecting the ternary alloys to flame tests and subsequently characterizing them via differential scanning calorimetry (DSC), optical microscopy, scanning electron microscopy in conjunction with energy- dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) analysis. The flame tests showed that the highest displacement was ca. 93%, with average austenite and martensitic start transformation temperature of 225°C and 222°C, respectively. XRD analysis revealed that the intermetallic phases responsible for the observed shape memory properties have substitutional Zn in the lattice occupied by Cu and Sn, leading to the formation of Cu(Zn,Sn) and Cu6(Zn,Sn)5 variants. The formation of these variants was attributed to the faster interdiffusion of Cu into Sn, driven by an activation energy of 34.82 kJ·mol−1. Five cycles of repeated torching–annealing revealed an essentially constant shape memory response, suggesting that the fabricated SMAs were consistent and sufficiently reliable for their intended service application.