Particle Dissolution and Recrystallization Progress of Al–Mg–Si–Cu Alloy during Solution Treatment

Abstract

Particle dissolution and recrystallization progress of Al–Mg–Si–Cu alloy during solution treatment at 555°C was studied by microstructure, hardness and electrical conductivity characterization, and analytical calculation in the present study. The results show that recrystallization and dissolution could occur concurrently during solution treatment, and the solution time has an appreciable influence on hardness, electrical conductivity, secondary phase particles and grain structure of the Al–Mg–Si–Cu alloy. As the solution time increases, the hardness decreases at first, and then increases, and almost remains constant finally; the electrical conductivity decreases sharply at first, and then decreases slowly, and almost keeps constant finally. In addition, the microstructure transforms from the deformation elongated bands to recrystallization equiaxed grains, and the particles are gradually dissolved with the increase of the solution time. The dissolution of the particles may be completed in the range of 120–300 s and the recrystallization was finished not exceeding 60 s. The predicted dissolution time by an analytical model combining classical diffusion-controlled dissolution equation for a single spherical particle and a John–Mehl–Avarami-like (JMA-like) equation is approximately 170 s, which is consistent with the experimental results.