J. Mater. Sci. Technol. ›› 2019, Vol. 35 ›› Issue (6): 957-961.DOI: 10.1016/j.jmst.2018.12.002

    Next Articles

Superb cryogenic strength of equiatomic CrCoNi derived from gradient hierarchical microstructure

Bin Gana, Jeffrey M. Wheelerb, Zhongnan Bic*(), Lin Liua, Jun Zhanga, Hengzhi Fua   

  1. a School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an, 710072, China
    b Laboratory for Nanometallurgy, Department of Materials Science, ETH Zürich, Vladimir-Prelog-Weg 5, Zürich, CH-8093, Switzerland
    c Central Iron and Steel Research Institute, No. 76 Xueyuannan Road, Beijing, 100081, China
  • Received:2018-07-01 Revised:2018-08-13 Accepted:2018-08-27 Online:2019-06-20 Published:2019-06-19
  • Contact: Bi Zhongnan
  • About author:

    1The authors contributed equally to this work.

Abstract:

This work demonstrates the effectiveness of a cryogenic torsional pre-straining for significantly improving the cryogenic strength of an equiatomic CrCoNi alloy. The origin of this phenomenon is elucidated by various microstructural characterization tools, which shows that the sequential torsion and tension tests lead to the observed hierarchical microstructure through the activation of different twinning systems and stacking faults. This gives rise to the significant increase in the yield strength from 600 MPa to 1215 MPa, while the fracture strain changes from 68% to 48%. The current study reveals that the incorporation of nanotwins architecture by shear deformation may constitute a viable strategy to tune the mechanical performance and, in particular, to dramatically increase the strength while keeping a good ductility.

Key words: Medium entropy alloy, CrCoNi, Torsion, Hierarchical microstructure, Strengthening