Form-free size distributions from complementary stereological TEM/SAXS on precipitates in a Mg-Zn alloy

Abstract: This work describes a multidisciplinary research methodology for quantifying the size distribution of nanoscale precipitates in polycrystalline alloys. Complementary transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS) are employed in a study of precipitate growth in an isothermally aged Mg-Zn alloy. TEM is used to identify the precipitate phases as rod-shaped \beta' particles and to determine their radii and aspect ratio. Subsequently, SAXS data obtained from bulk quantities of the alloy is interpreted via a novel Monte-Carlo method to obtain accurate, form-free size distributions. Good agreement was obtained between particle radii distributions measured by both methods, exemplifying the applicability of this complementary methodology to study precipitation in textured alloys containing particles anisotropic with well-defined orientation-relationships to the matrix.