Effects of an electric field applied during the solution heat treatment of the Al–Mg –Si–Cu alloy AA6111 on the subsequent natural aging kinetics and tensile properties

Abstract

Abstract The effects of an external dc electric field of 0 – 5 kV/cm, applied at 475 – 550 °C during solution heat treatment (SHT) to AA6111, on the subsequent natural aging kinetics and volume fraction of precipitated clusters were determined employing resistivity. The field increased the asquenched resistivity and that during natural aging, the effect being significant from 0 to ≈0.5 kV/cm and increasing only slightly, if at all, thereafter. An Avrami-type analysis of the natural aging kinetics gave n = 0.59 ± 0.2 and k = (1.2 ± 0.8) · 10– 2 min –1, relatively independent of SHT temperature and field strength. The field increased the volume fraction of precipitated clusters which occurred during natural aging. This was attributed to the increase in solubility during SHT produced by the field. Tensile properties equivalent to those obtained by the SHT at 550 °C without a field were obtained at 500 °C with a field of only 200 V/cm, representing a reduction of 50 °C in the nominal SHT temperature.