Reversion Characteristics in an Al-4wt%Cu Alloy

Abstract

The X-ray diffuse scattering intensity around the 110 reciprocal lattice point was measured in order to determine quantitatively the amount and size of precipitates during ageing and reversion. The precipitated phase was definitely determined by the aids of Laue X-ray photographs and the electron diffraction patterns. The electrical resistivity was carefully measured. When the alloy was aged for 1000 min at 373K, the GP zones precipitated with a mean diameter of 8.0nm. During the reversion, those zones dissolved perfectly above 458K, which is in good agreement with the result of Beton and Rollason. After the perfect dissolution of the GP zones, the Θ′ phase precipitated directly and heterogeneously. By ageing for 4000 min at 408K, the Θ″ phase precipitated with a mean diameter of 12.5 nm. When its aged alloy was reverted, the temperature at which the volume fraction of precipitates becomes minimum, but not zero, was 498K, where the successively precipitated Θ′phase exsisted already.