Ultrahard BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy formed by nanoscale diffusion-induced phase transition

作者：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^*

来源：JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY, 2022, 115: 29-39.

DOI：10.1016/j.jmst.2021.11.025

• High-entropy alloy
• Nanocrystalline
• Composites
• Diffusion-induced phase transition
• Mechanical
• Inert gas condensation

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 in-crease 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 con-tent (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 degrees C for 1 h. We present a systematic investigation of the relationship between the microstructure evolution and mechanical properties dur -ing annealing, and the corresponding micro-mechanisms in different annealing stages are revealed. The enhanced nanoscale thermal diffusion-induced phase transition process dominates the mechanical per-formance evolution of the nc-HEACs, which opens a new pathway for the design of high-performance nanocrystalline alloy materials.

• 单位
  南京理工大学