Abstract. The Cu- Al-Ni shape memory alloys have numerous industrial applications such as actuators, Cryofit hydraulic couplings, fire safety valves, etc. while the parts that are soaked in the seawater suffer severe corrosion that leads to worsening in the properties of the alloys. In the current research, the effect of adding titanium on the corrosion behavior of the shape memory alloys (Cu 13wt.%Al-4wt. %Ni) was studied. Titanium was added in different weight ratios (0.4, 0.8, and 1.2 wt.%) to the base alloy. The alloys were prepared using powder metallurgy, whereby the alloys were sintered with two stages of heating under Argon atmosphere, at 550? for (120 min.) and 950? for (180 min.) respectively. All the sintered samples are solution treated by heating the samples at 900 ? for (60 min.) followed by rapid quenching in ice water at ( 3 ~ 6)?. After that aging heat treatment has been done for quenched samples at 200 ? for (30 hrs.) followed by rapid quenching in iced water. Several tests such as microstructures observation and phase analysis using scanning electron microscope, energy dispersive spectrometer, and X-ray diffraction analysis have been done. Further, Corrosion behavior for all samples in aged conditions in 3.5%NaCl solution has been performed. Corrosion test results have shown that the highest corrosion resistance was found in the addition of (1.2 wt.% Ti) which gives the lowest corrosion rate (0.003 mpy) in 3.5% NaCl solution. Noted that the corrosion rate of the base alloy was (9.021)may. EDS analysis showed the chemical composition of the aged surface and also mapping images for the distribution of Cu, Al, Ni, and Ti elements on the surface. Phases formed on aged samples conditions are ?-Cu and AlCu3.
Conclusions
1. Results showed that powder metallurgy can successfully produce the Cu-Al-Ni alloy as a potential form of shape memory alloy.
2. Addition of 1.5 wt.%Ti to the base alloy (Cu-13wt. %Al-4wt. %Ni) reduced the corrosion rate by (300%) with respect to a reference sample in 3.5 wt.% NaCl solution.
3. The best value of corrosion current obtained from Cu-13wt. %Al-4wt. %Ni -1.2 wt.% Ti alloy was 0.008 ?A/cm2 compared with that of the reference sample 20.88 ?A/cm2 in 3.5 wt.% NaCl solution.
4. XRD analysis and SEM observation showed that the formed phases in age base alloy without and with Ti addition were ?-Cu and AlCu3.
5. Oxide phases that formed on Cu-Al-Ni -1.2wt.% Ti alloy after corroded in 3.5%NaCl are Cu2O and Al2O3