J. Mater. Sci. Technol. ›› 2020, Vol. 59 ›› Issue (0): 37-43.DOI: 10.1016/j.jmst.2020.04.039

• Research Article • Previous Articles     Next Articles

A new guide for improving mechanical properties of non-equiatomic FeCoCrMnNi medium- and high-entropy alloys with ultrasonic nanocrystal surface modification process

Timothy Alexander Listyawana, Hyunjong Leeb, Nokeun Parka,c,*()   

  1. a School of Materials Science and Engineering, Yeungnam University, 280 Daehak-ro, Gyeongsangbuk-do, 38541, Republic of Korea
    b Korea Institute of Industrial Technology, Incheon, 21999, Republic of Korea
    c Institute of Materials Technology, Yeungnam University, 280 Daehak-ro, Gyeongsan, Gyeongsangbuk-do, 38541, Republic of Korea
  • Received:2019-12-20 Revised:2020-02-21 Accepted:2020-04-19 Online:2020-12-15 Published:2020-12-18
  • Contact: Nokeun Park

Abstract:

Ultrasonic nanocrystal surface modification (UNSM) treatment on non-equiatomic medium- and high-entropy alloy (HEA) of Fex(CoCrMnNi)100-x is firstly introduced and its impact on microstructure and mechanical properties are revealed. By UNSM, severe plastic deformation-induced dislocation and deformation twins (DTs) arise at the topmost surface. Especially, Fe60(CoCrMnNi)40 (Fe60), which is classified as a medium-entropy alloy (MEA), exhibits ε-martensitic transformation. In the room temperature tensile test, a high strength of ~600 MPa and ductility of ~65 % elongation (strain to failure) is accomplished in Fe60. Initially formed DTs and ε-martensitic transformation by UNSM treatment plays a key role in retardation of necking point via both twinning-induced plasticity and transformation-induced plasticity. However, Fe20(CoCrMnNi)80 (Fe20) comparatively shows low strength of ~550 MPa and ~40 % elongation, owing to the low accommodation of DTs than Fe60. Our research will provide new guidelines for enhancing the mechanical properties of MEA and HEA.

Key words: High-entropy alloys, Ultrasonic nanocrystal surface modification, Deformation twin, Microstructures, Mechanical properties