Crystallographic Features of <11¯00> Axis Tilt Boundaries in a High Strain Rate Deformed Mg9Y Alloy

In this study, the microstructure evolution of solution-treated Mg9Y alloy during high strain rate deformation was systematically investigated. Abundant deformation bands were formed to subdivide the grain. The crystallographic features of these defomation bands, including the {112¯1} twin, twin-like tilt boundaries, {112¯2} twin and kink bands, were identified by characteristic misorientation angles along <11¯00> axis. The {112¯2} twin was observed for the first time in Mg alloys, and probably evolved from {112¯1} twin through lattice rotation along <11¯00> axis in this case. To accommodate strain in a short time, kink band boundaries with <11¯00> rotation axis were formed due to local lattice rotation and interacted with {112¯1} twin boundaries, resulting in the the formation of <11¯00> axis tilt boundaries with various misorientation angles. The lattice rotation process was attributed to the basal and pyramidal-II < c + a > dislocation slips under high strain rate deformation. These results will offer insight into microstructure evolution during high strain rate deformation and inspire the development of high-performance Mg alloys.