Influence of the nature of an electric field applied during the solution heat treatment of the Al-Mg-Si-Cu Alloy AA6111 on subsequent natural aging

Abstract

Abstract The effect of a “non-contacting” electric field (Method A) applied during the solution heat treatment of the Al – Mg – Si – Cu alloy AA6111 on subsequent natural aging measured by resistivity was determined and compared with that without field and with a field in which the specimen is connected to the positive terminal of the power supply (Method B(+)). Method A gave an increase in the level of the aging curve compared to that without field, but the increase was less than that with Method B(+). Neither field method had an effect on the general form of the aging curve, which was in accord with the Avrami equation with n = 0.49 and k = 0.02. The maximum resistivity for natural aging increased linearly with the as-quenched resistivity for the range in solutionizing temperatures (475 – 550 °C) without and with an electric field (0.2 and 2.5 kV cm−1) considered. This relationship gave: (a) the magnitude of the contribution of the insoluble constituents to the resistivity and (b) the ratio of the resistivity due to clusters of solutes formed during natural aging to that due to the as-quenched solute distribution. An electric charge on vacancy – solute atom clusters appears to be an important factor in the influence of an applied electric field on solubility.