Evaluation of Shape Memory Effect In Cu-Zn-Ni Shape Memory Alloy

Ni-Ti and Cu–based shape memory alloys, such as Cu-Zn-Al and Cu-Al-Ni, are presently available for commercial shape memory applications. Ni-Ti shape memory alloys exhibit better shape memory properties and good corrosion resistance than Cu-based alloys. However Ni-Ti in finished form is very expensive because of fabrication difficulties associated with melting and forming. In many applications, Cu-based shape memory alloys provide a more economical alternative to Ni-Ti in terms of melting and designing into desired form. Cu-Zn-Ni shape memory alloys in the range of 38- 55 wt. % of  Zinc and 0- 15 wt % of nickel, exhibiting β- phase at high temperature and manifesting shape memory effect upon quenching to lower temperatures, were prepared through ingot metallurgy route. The alloys undergo a martensitic transformation upon quenching from β- phase to lower temperatures. In the present study, Cu-Zn-Ni alloys were characterized for their microstructure using optical microscopy, the phases were determined by X-ray diffraction (XRD) and martensitic transformation behavior by differential scanning calorimetry (DSC) and shape memory effect. The alloys exhibit good ductility and shape memory effect. The results are given and discussed in detail.

Key words: Cu–Zn–Ni shape memory alloy, Transformation temperature and Shape memory effect.