title: Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility.
abstract: Grain refinement can make conventional metals several times stronger, but this comes at dramatic loss of ductility. Here we report a heterogeneous lamella structure in Ti produced by asymmetric rolling and partial recrystallization that can produce an unprecedented property combination: as strong as ultrafine-grained metal and at the same time as ductile as conventional coarse-grained metal. It also has higher strain hardening than coarse-grained Ti, which was hitherto believed impossible. The heterogeneous lamella structure is characterized with soft micrograined lamellae embedded in hard ultrafine-grained lamella matrix. The unusual high strength is obtained with the assistance of high back stress developed from heterogeneous yielding, whereas the high ductility is attributed to back-stress hardening and dislocation hardening. The process discovered here is amenable to large-scale industrial production at low cost, and might be applicable to other metal systems.
authors.affiliation: State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China; xlwu@imech.ac.cn ytzhu@ncsu.edu.
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;
authors.forename: Muxin
authors.initials: M
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;
authors.forename: Fuping
authors.initials: F
authors.lastname: Yuan
authors.affiliation: College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
authors.forename: Guilin
authors.initials: G
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China;
authors.forename: Yujie
authors.initials: Y
authors.lastname: Wei
authors.affiliation: College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
authors.forename: Xiaoxu
authors.initials: X
authors.lastname: Huang
authors.affiliation: School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China; Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695 xlwu@imech.ac.cn ytzhu@ncsu.edu.
authors.forename: Yuntian
authors.initials: Y
authors.lastname: Zhu
keywords: back-stress hardening; ductility; heterogeneous lamella structure; strain partitioning; strength