Improved Edge Quality for AZ31 Sheets Using Online Heating Rolling Technique

The edge quality of AZ31 sheets prepared by online heating rolling (O-LHR) technique under different rolling temperatures has been investigated. The AZ31 sheets are rolled from 3 mm to around 1 mm via four passes under three different temperatures. Each pass reduction keeps a constant about 25%. For comparison, a series of sheets are also rolled by conventional rolling (CR) under the same condition. The macroscopic observation for sheets rolled by both processes and microstructure examination for the rolled sheets via O-LHR are performed to characterize the edge cracking behavior. The results reveal that the edge quality of sheets after O-LHR is better than that through CR and remarkably improves with the increase in temperature. No obvious edge crack appears in AZ31 sheet rolled by O-LHR at a rolling temperature of 250 °C. This can be attributed to the enhanced dynamic recrystallization and the activation of non-basal slip, which results in a homogeneous microstructure at the edge.