Mechanisms of radiation-induced segregation in CrFeCoNi-based single-phase concentrated solid solution alloys

Abstract

Single-phase concentrated solid solution alloys have attracted wide interest due to their superior mechanical properties and enhanced radiation tolerance, which make them promising candidates for the structural applications in next-generation nuclear reactors. However, little has been understood about the intrinsic stability of their as-synthesized high-entropy configurations against radiation damage. Here we report the element segregation in CrFeCoNi, CrFeCoNiMn, and CrFeCoNiPd equiatomic alloys when subjected to 1250 kV electron irradiations at 400 °C up to a damage level of 1 displacement per atom. Cr/Fe/Mn/Pd can deplete and Co/Ni can accumulate at radiation-induced dislocation loops, while the actively segregating elements are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L1 0 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively. These findings are rationalized based on the atomic size difference and enthalpy of mixing between the alloying elements, and identify a new important requirement to the design of radiation-tolerant alloys through modification of the composition.

Single-Phase Concentrated Solid-Solution Alloys: Bridging Intrinsic Transport Properties and Irradiation Resistance

“…Furthermore, a trend of reducing RIS level has been observed with increasing compositional complexity, from NiFe, NiCoFe, NiCoFeCr, to NiCoFeCrMn . For all the observed RIS cases, as representatively shown in Figures 7c,d, Ni and Co tend to enrich, but Cr, Fe, and Mn prefer to deplete near the defects (grain boundaries, loops, and voids) (He et al, 2017;Lu et al, 2017;Yang et al, 2018).…”

“…No secondary phases have been observed in any of the above materials under ion irradiations (including NiFe,NiCoFe,NiCoFeCr,NiCoFeCrMn,FeNiMnCr 0.66 , and NiCoFeCrAl 0.1 ) at all conditions, suggesting a great phase stability. However, the electron-irradiated NiCoFeCrMn and NiCoFeCrPd thin foils (TEM samples) have shown L10 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively, even at a low dose of 1 dpa (He et al, 2017). While not being single-phase by itself, the FCC solid-solution phase portion in NiCoFeCrCu nanocrystalline sample also maintains high phase stability against electron irradiation at temperatures up to 500 • C (Nagase et al, 2015).…”

Science and technology in high-entropy alloys

“…It was found that the CoCrFeNiMn HEA did not change significantly after 773 K high-temperature and 3 MeV Ni ions irradiation, and the grains did not coarsen. High performance of HEA radiation-resistant materials provides a new idea for nuclear materials, and it has been used as the catalyst in the nuclear energy [97,[101][102][103]. Waseem et al [68] considered that the W x TaTiVCr as low/reduced-activation alloys have a promising future for fusion power plants.…”

Irradiation responses and defect behavior of single-phase concentrated solid solution alloys

“…He et al studied the phase stability and defect cluster formation in CoCrFeNi-based SP-CSAs due to 1250 keV electron irradiation at 400°C up to 1 dpa. 34 It was found that CoCrFeNi exhibits no detectable phase separation/decomposition. By contrast, FeCoCrMnNi and FeCoCrNiPd show L1 0 (NiMn)-type ordering decomposition and h001i-oriented spinodal decomposition between Co/Ni and Pd, respectively (as shown in Fig.…”

“…7), which is similar with the high energy electron irradiation. 34,43 The binary NiFe exhibits the largest loop size and lowest loop density, while NiCoFeCrMn presents the smallest loop size and lowest loop density. However, the ternary NiCoFe and quaternary NiCoFeCr exhibit comparable loop density and loop size.…”