Open AccessThe formation of sigma phase in the CoCrFeNi high-entropy alloys
Author(s) -
X J Wang,
Mengfei Xu,
N Liu,
L X Liu
Publication year - 2021
Publication title -
materials research express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.383
H-Index - 35
ISSN - 2053-1591
DOI - 10.1088/2053-1591/ac0a5c
Subject(s) - annealing (glass) , sigma , high entropy alloys , materials science , atomic radius , entropy (arrow of time) , thermodynamics , metallurgy , microstructure , chemistry , physics , organic chemistry , quantum mechanics
The as-cast CoCrFeNi high-entropy alloys show simple FCC structure and outstanding deformation ability at room temperature. Respectively, after 50% of deforming at room temperature and annealing at intermediate temperature range of 600 °C–800 °C for 2 h, CoCrFeNi alloys still show simple-phase FCC structure. It is noteworthy that CoCrFeNi high-entropy alloys can’t be strengthened by means of annealing, while deformation is an effective way to strengthen the alloys. It is investigated that the formation of sigma ( σ ) phase in high-entropy alloys is closely related to the difference of atomic radius ( δ ), the concentration of valence electron ( VEC ) and paired sigma-forming element ( PSFE ) content, and PSFE plays an crucial role. When PSFE > 40 at.%, 6.75 ≤ VEC ≤ 7.86, 4.0 ≤ δ ≤ 7.2, σ phase is prone to form in high-entropy alloys. In addition, alloying and processing route are two important factors that affect the sigma-formation in CoCrFeNi high-entropy alloys.