Ultrahard BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy formed by nanoscale diffusion-induced phase transition. (10th July 2022)

• Record Type: Journal Article
• Authors: Wang, Junjie; Kou, Zongde; Fu, Shu; Wu, Shangshu; Liu, Sinan; Yan, Mengyang; Ren, Zhiqiang; Wang, Di; You, Zesheng; Lan, Si; Hahn, Horst; Wang, Xun-Li; Feng, Tao
• Is Part Of: Journal of materials science & technology. Volume 115(2022)
• Page Start: 29
• Page End: 39
• Publication Date: 2022-07-10
• Subjects: High-entropy alloy -- Nanocrystalline -- Composites -- Diffusion-induced phase transition -- Mechanical -- Inert gas condensation; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2021.11.025
• Languages: English
• ISSNs: 1005-0302

Abstract

Abstract: In the current work, the BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy (nc-HEA) with ultra-high hardness was formed by nanoscale diffusion-induced phase transition in a nanocomposite. First, a dual-phase Al/CoCrFeNi nanocrystalline high-entropy alloy composite (nc-HEAC) was prepared by a laser source inert gas condensation equipment (laser-IGC). The as-prepared nc-HEAC is composed of well-mixed FCC-Al and FCC-CoCrFeNi nanocrystals. Then, the heat treatment was used to trigger the interdiffusion between Al and CoCrFeNi nanocrystals and form an FCC-AlCoCrFeNi phase. With the increase of the annealing temperature, element diffusion intensifies, and the AlCoCrFeNi phase undergoes a phase transition from FCC to BCC structure. Finally, the BCC-AlCoCrFeNi bulk nc-HEA with high Al content (up to 50 at.%) was obtained for the first time. Excitingly, the nc-HEAC (Al-40%) sample exhibits an unprecedented ultra-high hardness of 1124 HV after annealing at 500 °C for 1 h. We present a systematic investigation of the relationship between the microstructure evolution and mechanical properties during annealing, and the corresponding micro-mechanisms in different annealing stages are revealed. The enhanced nanoscale thermal diffusion-induced phase transition process dominates the mechanical performance evolution of the nc-HEACs, which opens a new pathway for the design of high-performance nanocrystalline alloy materials.