Unexpected crystallographic structure, phase transformation, and hardening behavior in the AlCoCrFeNiTi0.2 high-entropy alloy after high-dose nitrogen ion implantation

P. Jenczyk; D. M. Jarzabek; Z. Lu; E. Gadalińska; N. Levintant-Zayonts; Y. Zhang

Materials and Design 216 (2022) 110568-110568

Harsh environments, such as nuclear power plants, require the development of materials with stable properties when exposed to radiation/bombardment conditions. In this work, a bulk high-entropy alloy (HEA) was implanted with nitrogen ions accelerated at 50 kV to induce and study crystal structural defects. X-ray powder diffraction (XRD) showed that the studies HEA consisted of two phases—σ and body-centered cubic (BCC)—and underwent the σ to BCC phase transformation due to ion bombardment. Unexpectedly, XRD peaks of implanted samples could not be assigned to any known simple nitride, a finding that suggests the creation of new high- or medium-entropy ceramics. Studies of the mechanical and tribological properties with the use of nanoindentation and scratch tests revealed a hardening of both phases of the implanted surface and higher wear resistance. There were also surprising increases in the hardness-to-Young’s modulus ratio and elastic recovery for both phases. The results are promising not only for the nuclear applications, but also for space applications, mechanical engineering, and tribology.

DOI: https://doi.org/10.1016/j.matdes.2022.110568