Influence of the introduction of ceramic particles in Al–Cu alloys on GP zone formation

From thermoelectric power measurements combined with hardness and differential scanning calorimetry (DSC) experiments, it is concluded that in quenched Al–Cu matrix composites, Guinier–Preston zone formation occurs in a state of almost equilibrium vacancy concentration, owing to the capture of vacancies by the defects present in the matrix of the composite (dislocations or interfaces). Nucleation conditions are thus modified and precipitation kinetics significantly delayed, but the volume 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 conducted on quenched materials.