INFLUENCE OF THE INTRODUCTION OF CERAMIC PARTICLES IN AL-CU ALLOYS ONGP ZONE FORMATION

From thermoelectric power measurements combined with hardness and diff erential scanning calorimetry (DSC) experiments, it is concluded that in quenched AI-Cu matrix composites, Guinier-Preston zone formation oc curs in a state of almost equilibrium vacancy concentration, owing to the capture of vacancies by the defects present in the matrix of the c omposite (dislocations or interfaces). Nucleation conditions are thus modified and precipitation kinetics significantly delayed, but the vol ume fraction precipitated at the end of the process remains unchanged. It is also stressed that DSC experiments, which are commonly used to study the effects of reinforcement, may be misleading when they are co nducted on quenched materials. (C) 1998 Elsevier Science S.A. All righ ts reserved.