Capabilities of asymmetric rolling of single-layer and laminated materials made from aluminum and its alloys

Abstract

Asymmetric rolling of aluminum alloys is one of the methods for improving their mechanical and performance characteristics. Kinematic asymmetry during rolling is achieved by varying the roll speed ratios (V1 /V2). It is believed that when V1 /V2 > 3, the process of asymmetric rolling, by combining significant compression and shear deformations, approximates the processes of severe plastic deformation. It has been found that the majority of studies are based on data obtained within a limited roll speed ratio range, V1 /V2 < 2, in asymmetric rolling. This article examines the effects observed at V1 /V2 = 1÷7.7. The implementation of this condition became possible thanks to a unique scientific facility – the 400 laboratory-industrial asymmetric rolling mill at the Zhilyaev laboratory “Mechanics of Gradient Nanomaterials” at Nosov Magnitogorsk State Technical University Experiments were conducted on asymmetric thin-sheet rolling of aluminum alloys 2024, 5083, and 6061, as well as accumulative roll bonding to produce laminated sheet aluminum composites 5083/2024, 5083/1070, and 6061/5083. The disadvantages of asymmetric rolling compared to symmetric rolling were identified: sample failure was observed at single relative reductions of 37 % for layered sheet aluminum composites (5083/2024) and 40 % for thin-sheet aluminum alloys (6061). The nuances of material preparation for processing were described, including the necessity of cleaning and degreasing the alloy surfaces before bonding into a composite. The rolling temperature regimes were selected, determining cold asymmetric thin-sheet rolling (room temperature processing) and warm asymmetric accumulative roll bonding (heating of the workpieces in the furnace before rolling at 320–350 °C). A reduction in rolling force (by a minimum of 1.3 times), the ability to vary hardness (including an increase by a minimum of 30 %), and technological plasticity with changes in the roll speed ratios within the range of 2 to 7.7 were demonstrated. Options were proposed for reducing the processing cycles of aluminum alloys without compromising the quality of the finished product by reducing the number of rolling passes and annealing steps in the standard process scheme.