Precipitation processes in a Mg-Zn-Sn alloy studied by TEM and SAXS

The microstructural evolution of a Mg-Zn-Sn alloy was studied by combining X-ray diffraction (XRD), small angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) in order to determine the individual phases, their size and volume fraction of the alloy. Solutionized and aged samples are analysed in detail concerning the nucleation, growth, morphology, and stability of precipitate phases. In the aged samples, firstly MgZn2 particles with a rod-like shape form, and secondly plate-like MgSn2 precipitates. The MgZn2 phase shows a well-defined orientation relationship with the Mg matrix. The formation of two types of precipitates is responsible for the occurrence of two pronounced hardness maxima. The growth behaviour of the MgZn2 phase is determined by combining TEM and SAXS measurements and the results are compared to the Lifschitz-Slyozov-Wagner (LSW) theory.