Influence of Temperature Distribution on the Microstructure and Edge‐Cracking Behavior of AZ31 Sheets During Online Heating Rolling

The occurrence of edge cracks in magnesium alloy rolled sheets is closely related to the temperature distribution during rolling. However, the detailed temperature evolution of the sheet and its effects on edge cracking remain unclear. Herein, an online heating rolling (O‐LHR) temperature acquisition system is developed using embedded thermocouples. The temperature distribution of AZ31 alloy sheet at different rolling temperatures (180, 220, 260, and 300 °C) is quantified through mathematical expression and experimental validation, and its effects on the microstructure and edge‐cracking behavior are studied. The modified mathematical expression demonstrates good agreement with the experimental results in predicting the temperature evolution at the sheet's middle. Furthermore, increasing the rolling temperature reduces the temperature difference between the middle and the edge from 52.7–21.2 °C, correspondingly decreasing both the number and depth of the edge cracks. Specifically, the number of observed cracks decreases from 16 to 7, while the average crack depth is reduced from 0.9 to 0.2 mm. The O‐LHR improves the edge crack resistance of AZ31 sheets by reducing the temperature difference in the middle and the edge of the sheets.