Density gradient segregation of Cu at the Si2Hf/Al interface in an Al-Si-Cu-Hf alloy

Solute segregation at the Si2Hf/Al interface of an Al-Si-Cu-Hf alloy was investigated by combining high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectroscopy (EDS) and density functional theory (DFT) calculation. Density gradient segregation of Cu atoms was observed at the habit plane of the nanobelt-like Si2Hf phase, with the Cu concentrations gradually increasing to the Si2Hf/Al interface. This gradient segregation of Cu is found to be beneficial for decreasing both the strain and interfacial energies and thereby promoting the stabilization of the Si2Hf precipitates during heat treatment. This study provides an insight into the enhanced stability of Si2Hf precipitates in Al-Si-Cu-Hf alloy. [Display omitted]