Inhibitory effects of prefabricated crown on edge crack of rolled AZ31 magnesium alloy plate

The influence of prefabricated crown on edge cracking of rolled AZ31 magnesium alloy plate was investigated. Single-pass rolling experiments using four types of samples were performed. All specimens were produced by homogenizing the material for 2 h at 400 °C. Initial thickness of rolled plate was 10 mm, and the prefabricated convex metrics were 0 mm, 2.5 mm, 3.3 mm, and 4.1 mm, especially. Meanwhile, the influence of prefabricated crown on the cumulative maximum reduction of multi-pass rolling was also determined. Results showed that using prefabricated crown rolling process to produce AZ31 magnesium alloy slab could effectively control edge crack generation. Edge crack generation of prefabricated crown samples during rolling was associated with the maximum differential reduction value between center and edge region. Edge crack was not generated in the specimen with prefabricated convex metric of 4.1 mm after five passes rolling, which accumulated reduction up to 77%. Tiny grain shear band was found near edge crack in the microstructure, whereas the microstructure of center region was relatively uniform. Stress distribution was altered during prefabricated crown rolling process compared with using conventional rolling method. Such change in stress state was beneficial in promoting the synchronous extension of edge and center region of the metal. Generation of edge crack was eliminated or delayed in rolled plate after multi-pass rolling by prefabricated crown rolling process.