Study of Copper Effect on the Early Stage of Precipitation in Al-Mg-Si-Cu Alloys

Summary form only given. The development of solute clusters in the 6xxx aluminum alloys has been investigated by three-dimensional atom probe (3DAP). The presence of these clusters in the aluminum matrix is known to increase the hardness of the system and different responses to mechanical testing are obtained depending on the thermal history of the alloys before artificial ageing (i.e. room storage and pre-ageing). In addition, clusters formed before natural ageing play an important role on the subsequent precipitation of metastable phases that are responsible for hardening. In this study, the influence of copper addition, room temperature storage and pre-ageing on the very early stages of phase decomposition in two Al-Mg-Si(-Cu) alloys are investigated. The development of homo- and hetero-clusters as well as the chemical affinity between solute atoms are analysed by means of the pair correlation function calculated in 3DAP reconstructions