Effects of an external electric field applied during the solution heat treatment of the Al-Mg-Si-Cu alloy AA6111

The application of an external dc electric field during the solution heat treatment (SHT) of AA6111 Al alloy increased the as-quenched resistivity rho and hardness H-v. The increases represented reductions in SHT of 10-20 K required for a constant rho or H-v. Analysis of the results gave that the field reduced both the enthalpy and entropy of solution. The resulting reduction in Gibbs free energy gave increases of 0.03-0.04 at.% in solubility of Mg2Si (or Al-Mg-Si-(Cu)-vacancy complexes) at 400-600 degreesC, amounting to a factor of 33% increase in solubility at 400 degreesC and 6 % at 600 degreesC.