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Włoczewski M., Jasiewicz K., Jenczyk P., Gadalińska E.♦, Kulikowski K.♦, Zhang Y.♦, Li R.♦, Jarząbek D. M., AlCoCrFeNiTi0.2 High-Entropy Alloy Under Plasma Nitriding: Complex Microstructure Transformation, Mechanical and Tribological Enhancement,
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-025-07752-1, pp.1-17, 2025 Abstract:
In this study, the AlCoCrFeNiTi0.2 high-entropy alloy (HEA) was plasma nitrided to investigate the microstructure and mechanical properties of high-entropy nitrides formed in the surface layer of the bulk sample. XRD measurements revealed a BCC → FCC crystal structure transformation, with the σ phase disappearing and hexagonal aluminum nitride emerging. Further experimental studies on the nitrided samples, including SEM, EDS, and EBSD, uncovered element segregation into multiple FCC phases with similar lattice constants, such as the NaCl-type (AlCrCoFeNiTi0.2)N high-entropy nitride. These observations align with theoretical analysis based on KKR-CPA calculations. Additionally, plasma nitriding induced high surface porosity; however, micropillar compression testing combined with nanoindentation revealed localized areas with significant hardness. A substantial reduction in the coefficient of friction was also observed. These findings not only provide deeper insights into the nitriding process of complex alloys, like dual-phase HEAs, but also hold promise for further exploration in the manufacturing of super-hard surfaces with high-entropy nitrides, enhancing mechanical properties for applications in harsh environments. Affiliations:
| Włoczewski M. | - | IPPT PAN | | Jasiewicz K. | - | IPPT PAN | | Jenczyk P. | - | IPPT PAN | | Gadalińska E. | - | Institute of Aviation (PL) | | Kulikowski K. | - | other affiliation | | Zhang Y. | - | University of Notre Dame (US) | | Li R. | - | other affiliation | | Jarząbek D. M. | - | IPPT PAN |
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Jenczyk P., Jarząbek D.M., Lu Z.♦, Gadalińska E.♦, Levintant-Zayonts N., Zhang Y.♦, Unexpected crystallographic structure, phase transformation, and hardening behavior in the AlCoCrFeNiTi0.2 high-entropy alloy after high-dose nitrogen ion implantation,
Materials & Design, ISSN: 0264-1275, DOI: 10.1016/j.matdes.2022.110568, Vol.216, pp.110568-1-11, 2022Abstract:
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. Keywords:
high-entropy alloys, high-entropy ceramics, ion implantation, irradiation, phase transformation Affiliations:
| Jenczyk P. | - | IPPT PAN | | Jarząbek D.M. | - | IPPT PAN | | Lu Z. | - | University of Science and Technology Beijing (CN) | | Gadalińska E. | - | Institute of Aviation (PL) | | Levintant-Zayonts N. | - | IPPT PAN | | Zhang Y. | - | University of Science and Technology Beijing (CN) |
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