Special segregation of Cu on the habit plane of lath-like β′ and QP2 precipitates in Al-Mg-Si-Cu alloys

Abstract Cu segregation at the habit plane of lath-like β′ and QP2 precipitates for the over-aged Al-Mg-Si-Cu alloys were investigated by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). An even number spacing of Cu segregation ( d Cu ) was found in the habit plane of the lath-like β′ and QP2 precipitates, which is caused by the strong interaction between the segregated Cu atoms and the Si atoms within the precipitates. The Cu segregation at habit plane of these precipitates can accommodate the lattice misfit that exists between β´ and α-Al matrix.