PHASE-SEPARATION AND STRUCTURAL DEFECTS STUDIED BY SCATTERING TECHNIQUES

The basic equations for small-angle scattering (of X-rays and neutrons) are presented as they are currently used in the study of phase separation and defect agglomeration in solids. Small-angle scattering provides the spatial and temporal resolution necessary to study the kinetics and morphology of phase separation from very early to rather advanced stages. Some characteristic results on the decompositon of alloys, e.g. Au-Pt, Ni-Al, Ni-Ti, Ni-Al-Mo, are discussed in the light of current theoretical concepts of nucleation and growth, spinodal decomposition, power law scattering and scaling, and elastic interaction of precipitates. Vacancy agglomerates introduced by quenching or plastic deformation may also be revealed, as illustrated by measurements on quenched NiAl and fatigued Cu single crystals.