The assessment of GPB2/S′′ structures in Al–Cu–Mg alloys

Based on experimental data presented in the literature, we propose a new structure for GPB2/S′′ with the composition of Al10Cu3Mg3, which is aluminium-rich compared to S phase (Al2CuMg). The proposed structure is coherent with the fcc. Al matrix, is formed by the replacement of some Al atoms with Cu/Mg, and has orthorhombic structure (space group Imm2) with lattice parameters a = 0.405 nm, b = 1.62 nm and c = 0.405 nm. Simulated high resolution electron microscopy images and simulated diffraction patterns are compared with experimental data on a range of Al–Cu–Mg alloys. A good correspondence is found.