Revisiting the crystal structure of the equilibrium S (Al2CuMg) phase in Al-Cu-Mg alloys using X-ray absorption spectroscopy (XAFS).

Even though, the crystal structure of the intermediate (S’) and the equilibrium S (Al2CuMg) phase were subject of many investigations using mostly imaging or diffraction techniques, the results remain still controversial. Several reports indicate that the metastable S’ phase differentiates from the stable S phase only by their level of coherence and orientation relationship with the aluminum matrix while their crystal structures seem to be identical.