Effect of Ta Additions on the Microstructure,Damping, and Shape Memory Behaviour of Prealloyed Cu-Al-Ni Shape Memory Alloys

The influence of Ta additions on the microstructure and properties of Cu-Al-Ni shape memory alloys was investigated in this paper.The addition of Ta significantly affects the green and porosity densities; the minimum percentage of porosity was observed with themodified prealloyed Cu-Al-Ni-2.0 wt.% Ta. The phase transformation temperatures were shifted towards the highest values afterTa was added. Based on the damping capacity results, the alloy of Cu-Al-Ni-3.0 wt.% Ta has very high internal friction with themaximum equivalent internal friction value twice as high as that of the prealloyed Cu-Al-Ni SMA. Moreover, the prealloyed Cu-Al-Ni SMAs with the addition of 2.0 wt.% Ta exhibited the highest shape recovery ratio in the first cycle (i.e., 100% recovery), andwhen the number of cycles is increased, this ratio tends to decrease. On the other hand, the modified alloys with 1.0 and 3.0 wt.% Taimplied a linear increment in the shape recovery ratio with increasing number of cycles. Polarization tests in NaCl solution showedthat the corrosion resistance of Cu-Al-Ni-Ta SMA improved with escalating Ta concentration as shown by lower corrosion currentdensities, higher corrosion potential, and formation of stable passive film.