Influence of roll speed difference on microstructure, texture and mechanical properties of 7075 aluminum plates produced via combined continuous casting and rolling process
(Department of Mechanical Engineering, Faculty of Engineering, Bu-Ali Sina University, Hamedan 65178, Iran)
Abstract: The influences of the dissimilarity in the roll speeds on the microstructure, texture and mechanical properties of 7075 aluminum plates produced via combined continuous casting and rolling (CCCR) process were investigated. Several experiments were conducted with three different upper/lower roll rotational speed ratios (ω/ω0, ω is the upper roll rotational speed and ω0 is the lower roll rotational speed), namely 1:1, 1:1.2 and 1:1.4. It was found that the greatest dissimilarity in the roll speed (ω/ω0=1:1.4) improved the yield strength and ultimate tensile strength of 7075 Al plate in the rolling direction by 41.5% and 21.9%, respectively. Moreover, at a roll speed ratio of ω/ω0=1:1.4, the average grain size was decreased by 36% whereas the mean hardness of the transverse cross-section of the finally rolled plate was increased by about 9.2%. Texture studies also revealed that the more the difference in the roll speeds was, the greater the isotropy and the hardness of the final product were. Nevertheless, conducting CCCR operation with different roll speeds resulted in about 6% reduction in the elongation of the deformed plate.
Key words: continuous casting and rolling; 7075 Al alloy; roll speed difference; microstructure; mechanical properties; texture; anisotropy