Work-hardening behaviour of a heat-treatable AA7108 aluminium alloy deformed to intermediate strains by compression

This work is an experimental study of ageing and work-hardening considering various heat treatments of an AA7108 aluminium alloy in the as-cast and homogenized condition. Specimens have been exposed first to a solution heat treatment and a then to a two-step age-hardening to obtain different tempers. These tempers have been tested in an upsetting test applying state-of-the-art cold lubrication allowing intermediate strains to be reached before the onset of barrelling. The measured work-hardening response has been analyzed by fitting an extended Voce equation to the experimental stress–strain curves. With increasing overageing the stage III part of the stress–strain curve shrinks, and for the most overaged condition studied here, the stress–strain curve has reached a linear stage IV already at a strain of about 0.3. Interestingly, the slope of the stage IV curve then is lower than commonly reported for Al alloys. The microstructure and texture of the deformed material have been further investigated for a selection of tempers, and their influence on the work-hardening behaviour has been discussed.