The effect of aluminum concentration on the structure evolution and mechanical properties of Cu/Al composites produced by electron-beam additive manufacturing

Abstract

Electron-beam additive manufacturing with a simultaneous feed of two wires is used to produce Cu/Al composites with different contents of Al-12Si aluminum alloy. The obtained specimens are examined by optical microscopy and X-ray diffraction analysis and tested for uniaxial static tension. The introduction of 25 vol % Al-12Si is found to form a fairly homogeneous structure characterized by Cu dendrites and a small volume fraction of Cu9Al4 and Cu4Al intermetallic compounds on the dendritic cell boundaries. The increase of the volume fraction of Al-12Si in the copper alloy to 33 vol % is accompanied by the formation of Cu9Al4, Cu4Al, and Cu3Al intermetallics and an increase in their volume fraction. In the composite with 33 vol % Al-12Si, the Cu9Al4 phase becomes the main one, thus causing brittle fracture of the specimens without plastic deformation. It is shown that, with an increase in the volume fraction of Al-12Si to 30 %, ultimate strength increases significantly in the copper alloy (up to 695 MPa) and relative elongation decreases (down to 4 %) due to the increasing volume fraction of the brittle CuxAly intermetallic phases. The results of hardness measurements testify that the increase of Al-12Si content in the specimens from 25 to 33 vol % increases their microhardness significantly, namely from 1.38 to 4.35 GPa.