Effect of Stress State in Rolling Deformation Zone of AZ31 Magnesium Alloy Plate on Edge Cracking

The maximum damage value, damage distribution along the plate width and stress state in the deformation zone of flat and prefabricated edge crown plates were compared through numerical simulation of the single-pass rolling of AZ31 magnesium alloy at 350 °C. The results showed that the maximum damage exerted a certain weakening effect after the prefabricated edge crown, the weakening effect of the prefabricated crown was obvious, and the damage value decreased from 0.266 to 0.173. The maximum damage distribution along the plate width of the prefabricated crown was decreased by 40% from 0.25 to 0.15. The peak value of the three-direction stress and the rate of the stress change in the deformation zone were visibly reduced. At the same time, the change in the edge stress was reflected by a weakened tensile stress in the rolling direction, an increased normal compressive stress and an essentially unchanged compressive stress in the width direction. Rolling experiments found that a large number of microcracks appeared at the edges after flat plate rolling, the grains were relatively coarse, and the deformation ability was significantly different from that of the middle. After rolling of the prefabricated crown plate, no cracks formed at the edges, the grains were refined, and the deformation ability was significantly improved, which was basically consistent with the behavior in the middle part.