Improving the Corrosion Resistance of CuAlFeNi Shape Memory Alloy for Marine Applications

Abstract CuAlFeNi shape memory alloys (SMAs) were fabricated utilizing the stir-casting method. After that, the fabricated alloys were heat-treated at different temperatures. Microstructural analyses of the samples were performed using scanning electron microscopy attached with energy-dispersive X-ray spectroscopy, optical microscopy, and X-ray diffraction (XRD). The Brinell hardness was also assessed. The samples were then exposed to various electrochemical techniques in simulated seawater to determine their corrosion behavior and electrochemical characteristics. The findings demonstrated that the microstructure of the SMAs after annealing at 960°C and subsequent ice-water quenching was a martensitic phase. The results showed that, as the tempering temperature increased from 960/350°C to 960/650°C, the corrosion potential rose from − 0.68 to − 0.24 V Ag/AgCl , while the corrosion current density decreased from 32.0 µA cm −2 to 4.0 µA cm −2 . At the same time, the passive current density also decreased from (8.33 to 6.21) × 10 −4 A cm −2 . Electrochemical impedance tests showed that the treated sample at 960/650°C increased the charge transfer resistance while decreasing capacitance values in the double layers. These findings demonstrated that tempered SMAs had higher corrosion resistance than the as-cast alloy. The corroded morphologies revealed that, as the tempering temperatures rose, the corrosion degradation on the surface became smoother and more uniform, whereas the as-cast suffered from selective corrosion. Further, the XRD diffraction showed that the patina film is composed of Al 2 O 3 , CuO, and Cu 2 O phases.