Microstructure and mechanical anisotropy of the hot rolled Mg-8.1Al-0.7Zn-0.15Ag alloy

The microstructure and mechanical anisotropy of the hot rolled Mg-8.1Al-0.7Zn-0.15Ag (wt%) sheets were investigated. Dynamic precipitation and dynamic recrystallization (DRX) are the main features of the microstructures. Compared with the sheet rolled at 673 K, the sheet rolled at 633 K exhibits higher level of dynamic precipitates, finer grain size, more uniform microstructure and better strength. TEM observations reveal that the spherical Mg17Al12 phases which precipitate dynamically do not possess specific orientation with the matrix. Meanwhile, the migration of dynamic recrystallized (DRXed) grain boundaries is retarded by the pinning of fine particles, thereby leading to a remarkable grain refinement. DRX within the compression twins only appear in the alloy sheet rolled at 673 K and give rise to a weakened basal texture. The study on mechanical anisotropy behavior suggests that the reduced anisotropy of the sheet rolled at 633 K may ascribe to the activation of prismatic slip due to the presence of Mg17Al12 phases.