Strengthening and toughening bulk Ni2CoFeV0.5 medium-entropy alloy via thermo-mechanical treatment. (10th July 2023)

• Record Type: Journal Article
• Authors: Gu, Lei; Hou, Rui; Liu, Yi; Chen, Guang; Liu, Jihua; Zheng, Gong; Zhang, Ruisheng; Zhao, Yonghao
• Is Part Of: Journal of materials science & technology. Volume 151(2023)
• Page Start: 19
• Page End: 29
• Publication Date: 2023-07-10
• Subjects: Medium-entropy alloys -- Microstructures -- Strength and ductility -- Heterogeneous lamella structure -- Cold-rolling -- Annealing; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2022.11.051
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: Heterogeneous lamella (HL) structures were obtained in fcc Ni2 CoFeV0.5 MEAs. Most HL MEAs exhibited excellent strength and ductility synergy. Annealing-induced yield strength increase occurred in the as-rolled sample. The lattice friction stress ( σ 0 ) and Hall-Petch coefficient ( k ) are 87.3 MPa and 722.8 MPa μm 1/2, respectively. Abstract: Single-phase face-centered cubic (fcc) medium- and high-entropy alloys (MEAs/HEAs) have high ductility but low yield strength. In this work, the microstructures of single-phase fcc Ni2 CoFeV0.5 MEAs were tailored by cold-rolling and subsequent annealing and typical heterogeneous lamella (HL) structures composed of recrystallized micro-grain lamellae (with an averaged grain size of ∼4 μm) and non-recrystallized nano-/ultrafine-grain lamellae were obtained. Tensile tests revealed that most HL samples exhibited excellent strength and ductility synergy. The HL sample with ∼23 vol% recrystallized grains annealed at 590 °C for 1 h had a high yield strength of 1120 MPa and a good fracture elongation of 12.3%, which increased by 5% and 46%, respectively compared with those of as-rolled sample. Annealing-induced yield strength increase is attributed to high-density annealing twin boundaries (TBs) in the recrystallized grains, the annihilation of mobile dislocations inside the non-recrystallized grains, and extra hetero-deformation-induced strengthening produced by the HL structure. Hall-Petch relationship of Ni2 CoFeV0.5 MEA can be reasonably described by counting both TBs and grain boundaries, with lattice friction stress of 87.3 MPa and coefficient of 722.8 MPa μm 1/2 . Our work provides optional and controllable solutions for preparing MEAs/HEAs with excellent mechanical properties by low-cost and high-efficiency thermo-mechanical treatments. Graphical abstract: Image, graphical abstract