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

Cu segregation at the habit plane of lath-like beta' 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 beta' 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 beta' and alpha-Al matrix. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.