Phase identification of nanometric precipitates in AlSi9Cu alloy after remelting by laser beam

The aim of presented paper is an investigation of the structure changes in AlSi9Cu alloy after remelting by a laser beam. Scanning transmission electron microscopy was applied for structure characterization and precipitates phase identification. In the raw material, precipitates were larger and during remelting such precipitates were dissolved and very fast crystallization came next. Observed precipitates are generally uniform: in size, shape, and chemical composition. Generally, after remelting precipitates are not uniformly distributed in the whole sample but areas with dense, nanometric precipitates are common. Numerous volumes with elongated Ti precipitates, identified as Ti(Al_{1-x}Si_{x})₃, were found. Observed precipitate can strongly affect material properties (even in a case of law Ti concentration) because it may act as a crystal nucleus for other phases.