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.

Protecting car engines and controlling their temperature by using shape memory alloy as an automatic mechanical cooling sensor

“…The reason for this activity generated in SMA is the change in the molecular arrangement of the crystal structure resulting from the increase and decrease in temperature as in Figure 2 [5,6]. Martensite and austenite are two important phases in the transformation temperature of SMA, where austenite represents the active phase when the temperature is high and it is the phase of producing force and displacement, while martensite is the passive phase when the temperature is lower where it is soft and more capable of deformation [7,8].…”

Hysteresis gap-shrinking and structural effects of minor Al and Ti modifications on binary CuAl-based high-temperature shape memory alloys

“…In Cu-matrix only up to nearly 0.6 at% of Ti atoms make maximum twinning structure together with Cu atoms and such twinning decreases by higher amounts of Ti additions [25]. Doping binary Cu-Al-based shape memory alloys (SMAs) with small amounts of titanium to bring in higher transformation temperatures, recover thermal instability at high temperatures, and enhance ductility and strength by reducing grain size [26][27][28][29][30]. The minor (like less than %1 wt) amounts of Ti additions are often used as the ternary or quaternary grain refining alloying components which lead to the form of some Ti-based precipitations called X-phase [26,29,31].…”

“…Doping binary Cu-Al-based shape memory alloys (SMAs) with small amounts of titanium to bring in higher transformation temperatures, recover thermal instability at high temperatures, and enhance ductility and strength by reducing grain size [26][27][28][29][30]. The minor (like less than %1 wt) amounts of Ti additions are often used as the ternary or quaternary grain refining alloying components which lead to the form of some Ti-based precipitations called X-phase [26,29,31]. However, the influence of the direct use of Ti as the third (ternary) alloying element and more than %1 wt in binary CuAl alloys can give some more information about CuAl-based ternary or quaternary high-temperature shape memory alloys and their complicated and dynamic structures interdepend or interactive with thermal behavior, which of all are still under research to be fully understood.…”

Effect of 5.31Ti (at.%) content used as ternary in quaternary Cu-rich high-temperature shape memory alloy cast via arc melting

“…Ti element has been used as a grain refining and alloy strengthening element by adding minor amounts of it into the ternary Cu-based SMAs [7][8][9]. However, the low solubility of Ti in the Cu matrix leads to the form of Ti-rich X-phase precipitations [8]; therefore, its solid solubility and incorporation in the Cu-based alloy matrix is limited. Nevertheless, an extended solid solubility of Ti in melt-spun Cu-Ti alloy up to 7-8 wt.% (whereas by quenching up to 6 wt.%) has been demonstrated previously [10].…”