The generation and evolution of open volume defects in underaged and T3 Al-Cu-Mg alloy is studied with positron annihilation spectroscopy. During room temperature ageing the positron lifetime in plastically deformed, underaged material approaches the saturation lifetime of the undeformed material. Doppler-broadening results indicate that this behaviour can be attributed to diffusion and clustering of retained solute Cu atoms at the deformation defects, a process of relevance for the introduction of a self-healing mechanism in age-hardenable aluminium alloys.