Decomposition kinetics in Ni-Ti alloys

The decomposition of quenched Ni-Ti single crystals has been studied in beam by small-angle neutron scattering at 773, 813, and 853 K. Anisotropic scattering patterns were observed from the beginning and attributed to a preferred alignment of the decomposition products along 〈100〉. At 853 K the integrated intensity indicates that the composition of the precipitates remains constant after about 200 min. The Ti concentration estimated in this regime (16±3 at.%) is smaller than expected for a coherent, metastable γ’ precipitate (${\mathrm{Ni}}_3$Ti), possibly because of coherency strains.