Severe local lattice distortion in Zr- and/or Hf-containing refractory multi-principal element alloys

• Published in: Acta materialia 2020-01, Vol.183 (C), p.172-181
• Main Authors: Tong, Yang, Zhao, Shijun, Bei, Hongbin, Egami, Takeshi, Zhang, Yanwen, Zhang, Fuxiang
• Format: Article
• Language: English
• Subjects: Charge transfer; Density functional theory calculation; Local lattice distortion; Multi-principal element alloys
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2019.11.026

Whereas exceptional mechanical and radiation performances have been found in the emergent body-centered cubic (BCC) refractory multi-principal element alloys (RMPEAs), the importance of their complex atomic environment, reflecting diversity in atomic size and chemistry, has been largely unexplored at the atomic level. Here, we adopt a local structure approach based on the atomic pair distribution function measurements in combination with density functional theory (DFT) calculations to investigate a series of BCC RMPEAs. Our results demonstrate that all the analyzed RMPEAs exhibit local lattice distortions (LLD) to some extent, but a severe LLD, a breakdown of the 15% atomic size difference in Hume-Rothery rules, occurs only in the Zr- and/or Hf-containing RMPEAs. In addition, through the DFT calculations we show that charge transfer among the elements profoundly reduces the size mismatch effect in average to stabilize this energy-unfavorable severe LLD. The observed competitive coexistence between LLD and charge transfer demonstrates the importance of the electronic effects on the local environments in RMPEAs. [Display omitted]