J. Mater. Sci. Technol. ›› 2021, Vol. 85: 62-75.DOI: 10.1016/j.jmst.2020.11.081

• Research Article • Previous Articles     Next Articles

The effects of Y pre-alloying on the in-situ dispersoids of ODS CoCrFeMnNi high-entropy alloy

SeungHyeok Chunga, Bin Leeb, Soo Yeol Leec, Changwoo Dod, Ho Jin Ryua,*()   

  1. aDepartment of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
    bManufacturing Technology Office, Korea Institute for Rare Metal, Korea Institue of Industrial Technology, Get-Pearl Tower, Gaetbeol-ro 12, Yeonsu-gu, Incheon 21999, Republic of Korea
    cDepartment of Materials Science and Engineering, Chungnam National University, Daejeon 34134, Republic of Korea
    dNeutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
  • Received:2020-10-20 Revised:2020-11-19 Accepted:2020-11-21 Published:2021-09-20 Online:2021-02-08
  • Contact: Ho Jin Ryu
  • About author:*E-mail address: hojinryu@kaist.ac.kr (H.J. Ryu).

Abstract:

Oxide dispersion strengthened CoCrFeMnNi high-entropy alloys (ODS-HEAs) were prepared using two different powder preparation methods classified by yttrium addition strategy to investigate the effects of in-situ and ex-situ oxide dispersoid formation on the microstructure and mechanical properties. Systematic microstructural analysis was carried out by X-ray diffraction (XRD), electron backscattered diffraction (EBSD), high-resolution transmission electron microscopy (HRTEM), atom probe tomography (APT), and small-angle neutron scattering (SANS). Cryo-milled powder analysis, grain structure evolution after spark plasma sintering, dispersoid characteristics, and matrix/dispersoid interface structure analysis of the in-situ and ex-situ dispersoids within the high-entropy alloy (HEA) matrix were performed. The in-situ dispersoid formation was dominantly observed in the Y-alloyed ODS-HEA through the construction of a coherent interface relationship with complex chemical composition, leading to an increase in the Zener pinning forces on the grain boundary movement. ODS-HEA with in-situ oxide dispersoids enhanced the formation of ultrafine-grained structures with an average diameter of 330 nm at a sintering temperature of 1173 K. This study shows that the Y pre-alloying method is efficient in achieving fine coherent dispersoids with an ultrafine-grained structure, resulting in an enhancement of the tensile strength of the CoCrFeMnNi HEA.

Key words: Oxide dispersion strengthened (ODS) alloy, High-entropy alloy, In-situ oxide dispersoid formation, Microstructure, Mechanical property