Influence of electric field on microstructure and mechanical properties of an Al-Cu-Li alloy during ageing

• Electric field can accelerate the precipitation of β'/δ' and the growth of θ'.
• Electric field promoted the segregation of T1.
• Mechanical properties of alloy were improved by electric field during ageing.
• A vacancy-atom complex diffusion model successfully explains the phenomenon.

The effect of an electric field on the microstructure and mechanical properties of an Al-Cu-Li alloy was investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microhardness tests, electric conductivity tests, and tensile tests. The results show that the field-aged sample exhibited a shorter stable hardening plateau period and an earlier peak-aged stage than the field-free-aged sample. Also, the hardness and conductivity of the field-aged sample during the hardening plateau interval were generally greater than that of the field-free-aged sample. This might be due to the fact that the electric field promoted the precipitation of the β'/δ' phase and accelerated the growth of the θ' phase. The improvement in mechanical properties of the field-aged sample was caused by the segregation of the T1 phase at the subgrain boundaries and the grain boundaries. A vacancy-atom complex diffusion model successfully explains the microstructure evolution and the change in mechanical properties of the alloy during the ageing process accompanied by an electric field.

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