Study of the stability and decomposition process of the β phase in Cu–Al–Ni shape memory alloys

The influence of precipitation processes on the characteristics of the martensitic transformation in two Cu–Al–Ni shape memory alloys processed by powder metallurgy has been analyzed. The Cu–14.37Al–4.2Ni (wt.%) alloy with a hypereutectoid composition undergoes a low-temperature martensitic transformation, Ms < 100 °C. On the other hand, the Cu–14.15Al–3.25Ni (wt.%) near eutectoid composition undergoes a high-temperature martensitic transformation, Ms > 110 °C. The evolution of the kind of induced martensite, hysteresis and transformation temperatures as a function of thermal history has been studied by differential scanning calorimetry. Also, resonant ultrasound spectroscopy allows changes to be monitored of elastic constants during the evolution of the microstructure. Finally, a comparative analysis of the behavior of both alloys has been made.