Abstract
In this work, a 74.6 mm thick plate cast from 7075 Al alloy was subjected to two double-thermomechanical-treatment processes. The first of these processes includes FA-ITMT and a proposed new technique. In FA-ITMT homogenization, hot rolling, recrystallization, and finally hot rolling again are carried out. The proposed new technique involves recrystallization using a suitable time, temperature and cooling medium which gives good strength without decreasing the ductility, hot and cold rolling, then recrystalization under the same conditions. The second of these processes involves the FA-ITMT process associated with a newly developed FA-ITMT process, the latter containing four steps: (i) solid-solution heat-treatment; (ii) over-aging; (iii) hot- and cold-rolling; and (iv) recrystalization. A detailed study of the microstructure and mechanical properties was carried out and their interrelations were analysed, the results revealing that both of the two double-thermomechanical-treatment processes mentioned above led to improvement in strength and ductility simultaneously, associated with a refinement of the grain size. There was an increase in the ultimate tensile strength of up to 84.3%, an increase in the yield strength of up to 116.7%, and also an increase in ductility of up to 287.5%, associated with a decrease in the grain size from 45 to 16 μm. The first technique gave a good combination of strength and ductility. Also, the cold deformation accelerates the recrystallization rates, hence, fine grains can be obtained.
Published Version
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