A novel Ni-alloyed Cu-Al-Ga-Fe shape memory alloy with excellent shape recovery performance

In this study, a novel Ni-alloyed Cu-Al-Ga-Fe single crystal alloys were reported for the first time. The microstructure, martensitic transformation, shape memory effect, and superelasticity of Cu-12.5Al-4Ga-3Fe-xNi (x = 2, 3, 5) and Cu-13.5Al-4Ga-3Fe-xNi (x = 3, 4, 5) were investigated. The results show that Cu-12.5Al-4Ga-3Fe-xNi (x = 2, 3, 5) single crystals consist of the parent phase, 18R martensite, and β(FeAl) nano-precipitates. As the increase in Al content, Cu-13.5Al-4Ga-3Fe-xNi (x = 3, 4, 5) single crystals consist of the parent phase, γ1(Cu9Al4) phase, and β(FeAl) nano-precipitates. The martensitic transition finishing temperatures (Mf) of 12.5Al alloys are all higher than room temperature, while the reversible martensitic transition finishing temperatures (Af) of 13.5Al alloys are all lower than room temperature. Cu-12.5Al-4Ga-3Fe-3Ni single crystal shows the highest SME of 7.6% with 100% strain recovery. Similarly, the Cu-13.5Al-4Ga-3Fe-3Ni single crystal demonstrated the highest superelasticity of 11%. Additionally, the Cu-13.5Al-4Ga-3Fe-3Ni single crystal maintained 100% strain recovery even after 4500 cycles of compression deformation at 6%, although the critical stress of stress-induced martensite decreased with each cycle. These findings suggest that the Cu-Al-Ga-based shape memory single crystal alloys obtained in this study have promising applications in driving response devices.