Study of X-phase formation on Cu-Al-Ni shape memory alloys with Ti addition

Abstract

Cu-based shape memory alloys are used in various applications due to their attractive shape memory effect, easier process and cheaper cost. Cu-Al-Ni SMAs are one of the well-known Cu-based shape memory alloys because of their capability in demonstrating shape memory effect, damping behaviour, and thermoelastic martensitic transformation. In this paper, the effect of Ti addition on the phase transformation temperatures and microstructures of Cu-Al-Ni SMA was investigated. The Cu-Al-Ni alloy specimens were casted with the addition of titanium (Ti) using an induction furnace. Transformation temperature of the alloy was studied by differential scanning calorimetry. The evolution of the phases and microstructures was investigated by using the field emission scanning electron microscopy corresponding with energy dispersive spectroscopy and X-ray diffraction. It was found that the addition of Ti in the Cu-Al-Ni SMAs has increased the transformation temperatures. The results revealed that the addition of Ti led to the formation of a new phase into the microstructure known as X-phase. From the XRD result, it was indicated that the X-phase was AlNi2Ti and Cu3Ti compounds. It was also found that the alloy with 0.7wt% Ti has produced the most effective outcome of the transformation temperature (Ms: 233.16°C, Mf: 225.67°C, As: 229.85°C, Af: 239.25°C) due to the presence of X-phase in the microstructure. Further study will be carried out to investigate the application of this material and focus on the application of the material in damping application.