Role of pre-width reduction in deformation behavior of AZ31B alloy during break-down rolling and finish rolling

Abstract

Present study aimed at investigating the effect of introducing pre-width reduction (Pre-WR) on microstructure evolution and rolling formability variation during both the break-down rolling and finish rolling of AZ31B alloy. Different rolling routes relevant to the above two rolling processes were performed and compared. Results show that pre-induced twins by pre-rolling (8% thickness reduction) can significantly reduce the edge-cracking depth level during subsequent super-high reduction rolling (SHRR) (80% thickness reduction) through replacing the formation of shear bands by the promotion of the twinning-induced recrystallization to coordinate the severe deformation. However, the dominant behavior of twinning and twinning-induced DRX within the edge region induced a unique partial recrystallization with coarse grains and further a poor rolling formability in SHRR. Introducing more {101¯2} tensile twins at the edge by Inter-WR (a Pre-WR type with 10% width reduction) before the SHRR can significantly refine the grains and obtain almost a recrystallized homogeneous microstructure. It can also weaken the basal texture of the edge material and further decrease the number/depth level of edge crack by enhancing the activity of both non-basal slips and dominant continuous dynamic recrystallization (CDRX). During finish rolling, heavy twins and shear bands resulted in the larger edge crack level. The improvement of Pre-WR on rolling formability can be inherited to the strip finishing rolling process by evidently reducing the twins and shear bands.