The role of shear strain during Accumulative Roll-Bonding of multilayered composite sheets: Pattern formation, microstructure and texture evolution

Abstract

The present study was designed to determine the effect of shear strain on the macro- and microstructure and texture evolution in the AA1050/AA7050 Al multilayered composite sheets. The sheets were processed by Accumulative Roll-Bonding (ARB) and Asymmetric ARB (AARB) at 450 °C and 500 °C. The shear strain in the AARB process has a remarkable influence in achieving a macrostructural wavy-pattern, more than the flow behavior of the materials. For ARB, a flat-pattern with slight waviness was produced mainly due to flow incompatibility, as estimated by finite element simulation and observed by macrostructural analysis. In addition, friction at the surfaces and at the interfaces, and the strain distribution, together with the coarsening or dissolution of precipitates in the AA7050 layers have also influenced the shear banding and microstructure evolution in the sheets. A reduction in the texture intensity by AARB was observed. The grain refinement in the AA1050 layers was controlled by continuous dynamic recrystallization and static recovery during the thermo-mechanical cycles for both processing routes. The AA7050 layers presented a more complex grain refinement behavior that was influenced by dissolution of the η- and η′-phases, which was observed for both temperatures in the ARB. In contrast, the shear strain accelerated this dissolution kinetics and grain growth in the AA7050 layers of sheets processed by AARB.