Influence of relaxation of the atomic order in f.c.c.‐Ni–Al alloys on X‐ray diffuse scattering

Abstract

The atomic short‐range order (SRO) for the substitutional f.c.c.‐Ni–9 at.% Al single‐crystal solution is investigated using the X‐ray diffuse‐scattering method (supplemented by Monte Carlo simulation studies) and analyzing the salient features of the second‐order phonon diffuse scattering of X‐rays. As shown, in quenched state, the SRO corresponds to the presence in alloy of the static concentration waves with kX(0 0 1) and k(0 0 0.2) wave vectors. Initial SRO‐kinetics stage is attended by the noticeable increasing of the diffuse‐scattering intensities for wave vectors close to structural (Bragg) reflexes. Parameters of the time dependence of X‐ray diffuse‐scattering intensity for f.c.c.‐Ni–9 at.% Al alloy (after quenching) at low annealing temperature (373 K) are significantly different for different wave vectors generating the ordering and/or clustering processes.