A systematic study of the effect of interrupted ageing conditions on the strength and toughness development of AA6061

Recently it has been shown that for specific conditions interrupted ageing produces an improvement in mechanical properties of several heat treatable aluminium alloys. However, no systematic studies related to the heat treatment parameters leading to such improvements have been reported. The present work is a comprehensive study on the effects of the pre-interruption, interruption and post-interruption temperatures and times on the strength and toughness of AA6061. Each stage of the treatment is varied systematically and the effects were assessed through hardness, tensile and Kahn tear tests. Unlike earlier claims in the literature, for many combinations, no substantial improvement in strength and toughness over those values obtained via a regular T6 treatment was observed.