title: On the small angle twist sub-grain boundaries in Ti3AlC2.
abstract: Tilt-dominated grain boundaries have been investigated in depth in the deformation of MAX phases. In stark contrast, another important type of grain boundaries, twist grain boundaries, have long been overlooked. Here, we report on the observation of small angle twist sub-grain boundaries in a typical MAX phase Ti3AlC2 compressed at 1200 °C, which comprise hexagonal screw dislocation networks formed by basal dislocation reactions. By first-principles investigations on atomic-scale deformation and general stacking fault energy landscapes, it is unequivocally demonstrated that the twist sub-grain boundaries are most likely located between Al and Ti4f (Ti located at the 4f Wyckoff sites of P63/mmc) layers, with breaking of the weakly bonded Al-Ti4f. The twist angle increases with the increase of deformation and is estimated to be around 0.5° for a deformation of 26%. This work may shed light on sub-grain boundaries of MAX phases, and provide fundamental information for future atomic-scale simulations.
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Hu
authors.affiliation: Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH, 44106, USA.
authors.forename: Xun
authors.initials: X
authors.lastname: Zhan
authors.affiliation: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Wang
authors.affiliation: Science and Technology on Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials &Processing Technology, No. 1 South Dahongmen Road, Beijing 100076, China.
authors.forename: Yanchun
authors.initials: Y
authors.lastname: Zhou