J. Mater. Sci. Technol. ›› 2025, Vol. 216: 130-138.DOI: 10.1016/j.jmst.2024.07.042

• Research Article • Previous Articles     Next Articles

In situ atomic-scale observation of deformation-induced reversible martensitic transformation in a CrMnFeCoNi high entropy alloy

Junnan Jianga, Shufen Chub, Fan Zhangc,d, Mingwei Chene,∗, Pan Liua,f,∗   

  1. aShanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
    bNational Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composite, Shanghai Jiao Tong University, Shanghai 200240, China;
    cSchool of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China;
    dNational Key Laboratory of Science and Technology on Materials under Shock and Impact, Beijing 100081, China;
    eDepartment of Materials Science and Engineering, College of Engineering, Southern University of Science and Technology, Shenzhen 518055, China;
    fShanghai Jiao Tong University - JA Solar New Energy Materials Joint Research Center, Shanghai 200240, China
  • Received:2024-05-23 Revised:2024-07-06 Accepted:2024-07-28 Published:2025-05-01 Online:2024-08-23
  • Contact: *E-mail addresses: chenmw@sustech.edu.cn (M. Chen), panliu@sjtu.edu.cn (P. Liu)

Abstract: High entropy alloys (HEAs) have attracted much attention for their excellent mechanical properties stemming from diverse deformation mechanisms. Particularly, face-centered cubic (FCC) to body-centered cubic (BCC) martensitic transformation is crucial for enhancing the strength and plasticity of HEAs, particularly at cryogenic temperatures. However, the fundamental atomic mechanism underlying martensitic transformation remains elusive, and the impact of martensitic transformation on the mechanical properties of HEAs at room temperature is unknown. Here, we report in situ atomic-scale observation of a reversible martensitic transformation from FCC to body-centered tetragonal (BCT) and ultimately back to FCC in the nanostructured CrMnFeCoNi HEA at room temperature under deformation. This martensitic transformation is completed by the synergistic action of 90° partial dislocations slip on (111)FCC plane and atom shuffling, involving the periodic arrangement and slip of two 90° half Shockley partial dislocations a/12[$\bar{11}$2](111) and one 90° Shockley partial dislocation –a/6[$\bar{11}$2](111) on three successive (111)FCC atomic planes. Additionally, the reversible phase transformation induced by high stress dissipates strain energies and hinders crack propagation, thereby enhancing the fracture toughness of HEAs. Our findings contribute to a deeper comprehension of the martensitic transformation mechanisms in HEAs, offering valuable insights for improving their mechanical properties.

Key words: High entropy alloy, In situ deformation, Reversible martensitic transformation, Transformation mechanism