Nanostructure evolution of as‐cast magnesium alloy induced by ultrasonic impacting and rolling

The surface nanostructure evolution of as‐cast AZ31B magnesium alloy subjected to ultrasonic impacting and rolling process was investigated. Results show that deformation twinning greatly emerges in early stage to coordinate with deformation. As strain increases, interactions between twin and dislocation and dislocation itself occur. Dynamic recrystallisation is induced with nucleation sites originating from grain boundary intersections with serious dislocation pile‐up. Larger β‐particles serve as nucleation sites of dislocation sources and small‐sized substructures. With further refinement, β‐particles get smaller and unevenly distributed, yet a number of particles approximately locating in line can still intercept dislocations, making them turn into sub‐boundaries. The final grains with high angle boundaries are refined to 150–200 nm compared with the initial size of ∼500 μm.