Effect of hot rolling on microstructure, crystallographic texture, and hardness of AZ31 alloy

In this study, relationships between microstructure, texture, and hardness of hot-rolled AZ31 alloy were investigated. It was found that the grain size decreased into the ultra-fine domain after 60% hot deformation, reaching a grain size of 1 mu m. Several dynamic recrystallization (DRX) mechanisms activated after 40% and 60% deformations including discontinuous dynamic recrystallization (DDRX), twin dynamic recrystallization (TDRX), continuous dynamic recrystallization (CDRX), and particle stimulated nucleation (PSN). With increasing the thickness reduction, the intensity of basal texture first increased, then slightly decreased, and finally significantly increased to 15.7 multiple of random density. The average misorientation angle decreased when the thickness reduction increased owing to the formation of a very strong {0001} basal texture. With increasing the strains, the average microhardness increased because of decreasing grain size and increasing twin fraction and shear band density. There were no differences between the hardness values of RD-TD and RD-ND planes for AZ31 samples after 10% and 40% hot rolling and these samples were isotropic. After 60% deformation, the hardness of the RD-TD plane (73.5 HB) was higher than that of the RD-ND one (68.4 HB) that resulted in hardness anisotropy due to the generation of very strong basal texture.

Automated summary

The study found that hot-rolled AZ31 alloy exhibited ultra-fine grains after 60% deformation, as well as activation of various dynamic recrystallization mechanisms. As the thickness decreased, the grain size decreased, the intensity of basal texture increased, and accordingly, the hardness increased.