CONICET | Buscador de Institutos y Recursos Humanos

Cu-based shape memory alloys have been attracting attention due to their functional properties and potential applications in thermosensitive devices. The application of these alloys is still limited because of the low phases? stabilization and decomposition at high temperatures, which lead a shift on the martensitic transformation temperature due to a change in microstructure features. The thermodynamic stability and phase transformation should be well understood in order to keep the functionality of the material in a potential application. As many alloys of the Cu-Al-Ni system are defined as high temperature shape memory alloys due to high temperature phase transformation, this study aims to analyze the phases stability by means of heat treatments of the spray-formed Cu-11.35Al-3.2Ni-3Mn-0.5Nb (wt%) alloy. The microstructure and phase transformation were investigated by scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry and X-ray diffraction. It was found that the low temperature phase present in the alloy at room temperature is the monoclinic ? martensite and the high temperature phase are the austenite. After heat treatments at 250oC, the transformation temperatures increased and the hysteresis related to it decreased, but no changes in the microstructure compared to the as-cast samples was observed, which suggest the microstructure was stabilized by ordering and anhilation of quenched-in vacancies.