Diffuse scattering of Ni [sbnd]Al

Abstract

A Ni 8.9 at.% Al single crystal was aged at 775 K for one day to establish a state of thermal equilibrium and subsequently quenched to room temperature where it was investigated by diffuse neutron scattering. In the elastic coherent scattering, short-range order scattering was separated from linear displacement scattering. An abundance analysis of nearest and next-nearest configurations in crystals modelled on the basis of 21 Warren-Cowley short-range order parameters obtained from the experiment yields no signs for characteristic elements of the D7 structure (which has been suggested on the basis of electronic structure calculations), but for the L1 2 structure of the γ′ phase. A set of effective pair interaction parameters is found from the experimental data by using inverse Monte Carlo techniques. This set is not appropriate for estimating the temperature of congruent melting of Ni 3Al, presumably because the experimental effective pair interaction parameters depend on composition and/or temperature.