Determination of twinning path from broken symmetry: A revisit to deformation twinning in bcc metals. (1st September 2020)

• Record Type: Journal Article
• Authors: Gao, Yipeng; Zhang, Yongfeng; Wang, Yunzhi
• Is Part Of: Acta materialia. Volume 196(2020)
• Page Start: 280
• Page End: 294
• Publication Date: 2020-09-01
• Subjects: Deformation twinning -- Microstructure formation mechanism -- Transition path -- Crystallography -- Symmetry breaking; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2020.06.031
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Deformation twinning in crystals is one of the major strain carrier during plastic deformation, which plays a critical role in determining the mechanical properties of metals and alloys. One of the key issues to understand deformation twinning mechanisms is the determination of deformation path, which is critical for the calculations of twinning strain and critical shear stress. This work provides a new perspective on deformation twinning by systematically investigating the relationship between symmetry breaking and deformation path, with the purpose of establishing a theoretical foundation to identify the broken symmetries associated with twinning and predicting the twinning modes using group theory and graph theory. From a physical point of view, deformation twins can be regarded as one type of the so-called topological defects that are induced by symmetry-breaking. Taking BCC crystals as an example, we demonstrate how the presence of intermediate high symmetry states in the deformation strain space (strain calculated through lattice distortion) along the twinning path, such as FCC, HCP or orthorhombic state, can lead to different characteristic twinning modes. Our predictions not only agree well with classical theoretical analyses and experimental observations in BCC metals and alloys, but also reveal the origin of recently observed high-index twinning modes (such as {5 8 11} and {3 9 10} twins). This work may open a new avenue for analyzing deformation twinning through the symmetry breaking along twinning pathways. Graphical abstract: Three types of deformation pathways in BCC (B) crystals, with high-symmetry saddle structures of FCC (F), HCP(H) and orthorhombic (O) along different pathways. Image, graphical abstract