The Composition of Fine-Scale Precipitates in Al-Mg-Si Alloys

The compositions of intermediate precipitates in Al-Mg-Si alloys have been examined using atom probe field ion microscopy (APFIM), energy dispersive electron spectroscopy (EDS) and parallel electron energy loss spectroscopy (PEELS). It was found that the Mg:Si ratios in small, equiaxed precipitates, beta " precipitates and beta ' precipitates were clsoe to 1.1 (atomic). The Mg:Si ratio in a B' precipitate was approx0.9. The implications of these results to the understanding of the mechanical properties of Al-Mg-Si alloys are discussed.