Mechanical properties of aluminium-copper solid-phase welds

Abstract

The mechanical properties of aluminium-copper solid-phase welds have been examined in the as-bonded condition, and after heat treatment to produce intermetallic layers of up to 50 μm in thickness at the weld interface. The layers were grown both by continuous annealing and by thermal cycling. The presence of the intermetallic layers led to a reduction in the tensile, shear, and impact strengths of the joint. The impact strength was observed to be negligible for layer thicknesses greater than 2 μm. Thermal cycling had a more detrimental effect than an equivalent heat treatment by continuous annealing, and this was attributed to the build-up of thermal strains. Fractography showed that the fracture propagated between the brittle CuAl₂ and CuAl phases, and it was concluded that the existence of these brittle phases was principally responsible for the reduction in properties. Contrary to an earlier hypothesis, it was shown that porosity was not responsible for the poor joint properties after heat treatment.