Microstructure Characterization and Mechanical Properties of an AM60B Magnesium Alloy Sheet Prepared by the Double‐Pass High Strain Rate Rolling with Gradient Cooling

Abstract

AM60B magnesium alloy sheets with excellent mechanical properties are prepared by a double‐pass high strain rate rolling (HSRR) with gradient cooling from 370 to 340 °C. A bimodal lamellar structure, consisting of fine dynamically recrystallized grains, shear bands and fine precipitates, is obtained after the second‐pass HSRR. Formation mechanisms of shear bands are studied in depth. The results show that the formation of shear bands are closely related to the high‐density intersected twin lamellae, boundaries of initial coarse grains and the extensive dynamic recrystallization (DRX), respectively. It is also clarified that the HSRR process of the coarse grained AM60B alloy is dominated in succession by the twinning deformation stage and the following shear bands flow stage. Dynamic precipitation behavior is induced in the double‐pass HSRR process. The DRX is promoted by fine precipitates, resulting in local refinement of the HSRR'ed microstructure. Moreover, the weak basal texture is obtained with peak intensity less than 10. The high‐density twins, DRX and shear bands are suggested as main causes for the basal texture weakening. An outstanding matching between tensile strength and ductility at room temperature are obtained owing to the bimodal lamellar structure and the weakened basal texture.