Martensitic transformation characteristics, mechanical properties and damping behavior of Cu–Al–Ni shape memory alloys: A review of their modifications and improvements

Copper-based shape memory alloys (SMAs) have recently been introduced as a viable alternative to Ni–Ti SMAs. This is attributed to the fact that Cu-based SMAs are cheaper than Ni–Ti SMAs and exhibit satisfactory shape memory properties. Of these materials, Cu–Al–Ni SMAs have been widely used as they possess high thermal resistance and good mechanical properties. The concentration of Al and Ni is the most important factor determining the martensite type and transformation temperatures of these SMAs. Furthermore, thermal treatment, including quenching and aging, significantly affects the microstructural evolution and martensitic transformation (MT) temperatures of Cu–Al–Ni SMAs. Modifying the formed martensite phases and MT temperatures is possible by controlling the quenching rate and ageing temperature. Damping ability is one of the distinct advantages of these Cu-based SMAs, which has been modified and improved by many researchers. Plastic deformation is an effective method of evolving the microstructure of Cu–Al–Ni SMAs and improving their mechanical properties. Therefore, this present study examines the effect of alloy composition and thermal treatment on the MT temperatures and the microstructural evolution of Cu–Al–Ni SMAs. It also discusses the solutions to control the damping behavior of Cu-based SMAs, as well as the role of plastic deformation in improving the different properties Cu–Al–Ni SMAs. Lastly, additive manufacturing (AM) is proposed as a modern method of producing porous Cu–Al–Ni SMAs since it grants the possibility of controlling the porosities more efficiently.