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 AI-Cu alloy and in an Al-Mg-Si alloy on the modification of the kinetics of zone form ation are compared. Thermoelectric power measurements, performed on th e unreinforced and reinforced alloys, show that the kinetics of Guinie r-Preston zone formation are significantly retarded in the AI-Cu matri x composite, while they are only slightly modified in the Al-Mg-Si mat rix composite. This difference may be attributed to the trapping of va cancies by normal sinks (dislocations and interfaces) in the Al-Cu mat rix, while the solute-vacancy pairs formed in the 6061 matrix are rapi dly incorporated in the initial clusters, after participating in the p rocess of zone formation. (C) 1998 Elsevier Science S.A. All rights re served.