**Abstract**

Cu-Al-Ni shape memory alloys (SMAs) have been developed for hightemperature applications due to their ability to return to pre-deformed shape after heating above the transformation temperature, as well as these alloys have a small hysteresis and high transformation temperature comparing with other shape memory alloys. Adding some of the alloying elements such as Ti, Mn, Be, Zr and B or changing the interior content either Al or Ni by increasing/decreasing may have a significant effect on the phase transitions and enhance the mechanical properties of these alloys. However, the martensite phase transformation is the most important factor, which can be changing the whole properties of Cu-Al-Ni SMAs, where this phase is mainly affected by the alloying elements additions. This chapter reviews the effect of alloying elements on the phase transitions and the enhancement of the mechanical properties of this alloy.

**Keywords:** shape memory alloys, martensitic transformation, Cu-Al-Ni, grain refinement, alloying elements
