High temperature β phase decomposition process in a Cu–Al–Ni shape memory alloy

The atomic order and the precipitation processes of the metastable β phase during heating in a Cu–13.15 wt.% Al–3.25 wt.% Ni shape memory alloy processed by powder metallurgy, have been studied by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and in situ neutron powder diffraction. The transformation temperatures and activation energies have been determined by DSC. The Rietveld analysis performed on the neutron diffraction spectra allows determining the kind of order, the volume fraction of the different precipitated phases and their evolution during heating. Also, the influence of the Ni,Al-rich phase precipitation in the characteristic martensite–austenite transformation has been studied.