Mechanisms of interaction controlling the kinetics of zone formation in metal matrix composites: comparison of the effect of the reinforcement in Al–Cu and Al–Mg–Si matrix composites

The effects of the presence of ceramic particles in an Al–Cu alloy and in an Al–Mg–Si alloy on the modification of the kinetics of zone formation are compared. Thermoelectric power measurements, performed on the unreinforced and reinforced alloys, show that the kinetics of Guinier–Preston zone formation are significantly retarded in the Al–Cu matrix composite, while they are only slightly modified in the Al–Mg–Si matrix composite. This difference may be attributed to the trapping of vacancies by normal sinks (dislocations and interfaces) in the Al–Cu matrix, while the solute–vacancy pairs formed in the 6061 matrix are rapidly incorporated in the initial clusters, after participating in the process of zone formation.