A geometrical model for grain boundary migration mediated formation of multifold twins

YB Chen and SC Zhao and QS Huang and Q Zhu and KX Song and HF Zhou and JW Wang, INTERNATIONAL JOURNAL OF PLASTICITY, 148, 103128 (2022).

DOI: 10.1016/j.ijplas.2021.103128

The formation of multifold twins in nanocrystalline face-centered-cubic metals and alloys was frequently ascribed to a grain boundary (GB) mediated process. However, the geometrical requirement for the formation of multifold twins remains largely unclear. In this work, using combined in situ nanomechanical testing and atomistic simulation, we show that multifold twins can be generated through the migration of GBs associated with intersecting twin boundaries (TBs). We systematically evaluate a number of factors, including deformation geometry, loading condition, and coordinated deformation between GB and TB, that influence the underlying formation mechanisms. Such GB migration mediated formation of multifold twins exhibits a strong dependence on TB orientation (polarity) at GB-TB intersections and matrix orientation. Based on experimental observations, a general geometrical model is proposed to further reveal the intrinsic and extrinsic factors controlling the formation of multifold twins, which helps to establish a comprehensive map for the origin of multifold twins in nanocrystalline metals and also provides an accessible guidance for designing multifold twin structures in materials with high strength and good ductility.

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