Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility

By Xiaolei Wu, Muxin Yang, Fuh-Gwo Yuan, Guilin Wu, Yujie Wei, Xiaoxu Huang, Yuntian Zhu. Proceedings of the National Academy of Sciences of the United States of America, 2015

1,751 citations recorded by the source corpus.

Significance For centuries it has been a challenge to avoid strength–ductility trade-off, which is especially problematic for ultrastrong ultrafine-grained metals. Here we evade this trade-off dilemma by architecting a heterogeneous lamella structure, i.e., soft micrograined lamellae embedded in hard ultrafine-grained lamella matrix. The heterogeneous deformation of this previously unidentified structure produces significant back-stress hardening in addition to conventional dislocation hardening, rendering it higher strain hardening than coarse-grained metals. The high back-stress hardening makes the material as strong as ultrafine-grained metals and as ductile as coarse-grained metals. 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.

Subfields: Materials Chemistry, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/f1557716af286c4a4d2562f1ddddeec1ec41f404

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Materials Chemistry

1. Yuntian Zhu
2. Xiaolei Wu
3. R. Valiev
4. I. Ovid’ko
5. Xiaozhou Liao
6. Huajian Gao
7. Yonghao Zhao
8. Ting Zhu

In Mechanical Engineering

1. Yuntian Zhu
2. Xiaolei Wu
3. R. Valiev
4. I. Ovid’ko
5. Xiaozhou Liao
6. Yonghao Zhao
7. Huajian Gao
8. X. An

Citations in the corpus

• Critical microstructures and defects in heterostructured materials and their effects on mechanical properties (2020, methodology): “Partial recrystallization by annealing is an effective procedure for processing hetero-structured materials; readers are referred to the reference [12,58] for details.”
• Back stress strengthening and strain hardening in gradient structure (2016, background): “In a heterogeneous structure, strain will be inhomogeneous but continuous, producing strain gradients, which needs to be accommodated by GNDs.[23,25–27] It has been observed that back stress strengthening and back stress strain-hardening are primarily responsible for unprecedented combination of str”
• Dense dispersed shear bands in gradient-structured Ni (2020, background): “In addition, the dislocation pile-up near this elastic/plastic interface also contributes to stress concentration (Wu et al., 2015; Zeng et al., 2016).”
• Additional hardening in harmonic structured materials by strain partitioning and back stress (2018, background): “Several studies [10,21] reported the back stress hardening in heterogeneous structures, such as heterogeneous lamella structure.”