First-principles calculations of Ag addition on the diffusion mechanisms of Cu–Fe alloys

• The effect of Ag addition on the diffusion mechanisms of aging precipitation processed Cu–Fe alloys was investigated.
• Activation energy for diffusion calculations revealed that Ag atom significantly reduced the diffusion barrier and diffusion activation energy of Fe.
• The calculation gives way to find other suitable alloying elements for preparation of high strength and high conductivity Cu–Fe alloys.

The effect of Ag addition on the diffusion mechanisms of aging precipitation processed Cu–Fe alloys were investigated by first-principles calculations. The calculation of solute–solute binding energies accurately revealed an attractive binding for the Fe–Fe at the first NN site, and Ag–Ag at the first NN site as well as the second NN site, however the Fe–Ag interactions are repulsive both at the first NN and the second NN distance. The investigation of binding energy between X and V (X represents Fe or Ag and V a vacancy) showed that vacancy is more likely to be in the proximity of the solute Ag atom, and the addition of Ag to dilute Cu–Fe system will increase the local vacancy concentration close to a Ag–Fe dimer. The calculated migration energy for an X–V exchange indicated that the Ag atom diffused more easily in Cu than Fe atom; and the addition of Ag decreased the energy of the transition state, thereby significantly reduced the migration energy of Fe. The results agree well with the available experimental observation. The calculation gives way to find other suitable alloying elements for preparation of high strength and high conductivity Cu–Fe alloys or in situ composites.