Small-angle neutron scattering and phase separation in alloys

The basic principles of small-angle neutron scattering and the two-phase model, frequently used for the interpretation of scattering data, are presented. Some studies on phase separation in alloy single crystals serve to illustrate the possibilities of the method. Small-angle neutron scattering of Ni-rich Ni-Ti studied during ageing at elevated temperatures indicates a complex sequence of phases during decomposition, involving two stages of metastable coherent precipitation preceding the formation of the stable hexagonal phase.