Evolution of microstructure, texture, and mechanical properties in a twin-roll cast AA6016 sheet after asymmetric rolling with various velocity ratios between top and bottom rolls

Abstract

In this paper, we report the evolution of microstructure, texture, and mechanical properties of an AA6016 sheet prepared by twin-roll casting and subsequent asymmetric rolling (ASR). By controlling the velocity ratio (VR) of upper and lower rollers, it is determined that a strong shear strain is induced along the sheet thickness during the ASR process, which results in the formation of shear texture with a {111}//normal direction (ND). When the deformation sheets are annealed at 330 °C, the number and size of grain nuclei are increased with an increase in VR after partial recrystallization. When the sheets are completely recrystallized, different recrystallization mechanisms in symmetrically rolled (SR) and ASR sheets can be determined. The main recrystallization mechanism of the SR sheet is characterized as discontinuous recrystallization (DRX), while continuous recrystallization (CRX) contributes to the development of recrystallization in the ASR sheet, which is accompanied by the formation of finer-grain-band/ultrafine grains. Moreover, compared to that of annealed SR sheets, the shear texture ({111}//ND) of the annealed ASR sheet is enhanced during the nucleation and grain growth of recrystallization while the cube texture weakens, which results in a distinct increase in the Lankford coefficient for the annealed ASR sheet.