Simulation of multipass hot rolling of AA 6082 aluminium alloy

Multipass hot rolling of AA 6082 aluminium alloy were investigated by means of the simulative technique based on multistage hot torsion tests, performed on a hydraulically powered servo-controlled torsion machine. Three different test procedures, characterized by a linear decreasing temperature (from 525 to 300°C), a constant time between two subsequent deformations (20, 60 or 300 s) and a cumulative strain of 6.4 (number of passes equal to 16 or 32), were used: a) with constant strain rate on the specimen surface and constant strain per pass, b) with a linear increasing strain rate with a strain rate jump after each pass and constant strain per pass, c) with linear increasing strain rate and decreasing strain per pass. This allowed to simulate the rolling schedules for many combinations of process parameters. The influence of static and dynamic control parameters on the flow behaviour of the alloy was investigated in detail by analysing the flow curves. In particular, the envelope curves are influenced by the interpass time even if, at high temperatures, no significant effect is observed. The effect of the strain per pass differs from the one expected due to the strengthening effect produced by the static precipitation of second phase particles that is more enhanced as pass strain decreases. The strain rate path affects the envelope curves due to the strong influence of temperature on the constitutive parameters; finally, a more pronounced effect is produced by the strain path since early stages performed with larger pass strain values, owing to the more effectiveness of the dynamic restoration processes, lower the envelope curves.