Crystallographic features of 11¯00 axis tilt boundaries in a high strain rate deformed Mg 9Y alloy

In this study, the microstructure evolution of solution-treated Mg 9Y 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 { 11 2 ¯ 1 } twin, twin-like tilt boundaries, { 11 2 ¯ 2 } twin and kink bands, were identified by characteristic misorientation angles along < 1 1 ¯ 00 > axis. The { 11 2 ¯ 2 } twin was observed for the first time in Mg alloys, and probably evolved from { 11 2 ¯ 1 } twin through lattice rotation along < 1 1 ¯ 00 > axis in this case. To accommodate strain in a short time, kink band boundaries with < 1 1 ¯ 00 > rotation axis were formed due to local lattice rotation and interacted with { 11 2 ¯ 1 } twin boundaries, resulting in the the formation of < 1 1 ¯ 00 > axis tilt boundaries with various misorientation angles. The lattice rotation process was attributed to the basal < a > 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. • Multiple < 1 1 ¯ 00 > axis tilt boundaries are formed in the SHPBed Mg 9Y alloy. • The 11 2 ¯ 2 twin boundary can be evolved from the 11 2 ¯ 1 twin boundary via lattice rotation. • The intersection of < 1 1 ¯ 00 > tilt boundaries can subdivide the grain effectively. • The homogeneous strain can be achieved by the twin mesh microstructure.