Radiation-induced segregation(RIS)is a typical non-equilibrium process that can dramatically alter the behavior of defect sinks and material properties under irradiation.However,RIS mechanisms have been rarely studied around small He bubbles owing to the technical challenges involved in direct measure-ments of local chemistry.Here,using state-of-the-art atom probe tomography,we report the RIS behavior near He bubbles in the FeNiCoCr high-entropy alloy that indicates Co segregates most strongly,followed by weaker Ni segregation,whereas Fe and Cr are depleted almost to the same degree.Exceptionally,the magnitude of Co segregation around He bubbles is higher than previously measured values at voids and dislocation loops.Electron energy-loss spectroscopy was used to measure the He density and pressure inside individual bubbles.We demonstrate that He bubbles are over-pressurized at the irradiation tem-perature that could result in the vacancy bias and the subsequent vacancy-dominated RIS mechanism.First-principles calculations further reveal that there are repulsive interactions between He and Co atoms that may reduce the frequency of Co-vacancy exchange.As a result,He atoms likely retard Co diffusion via the vacancy mechanism and enhance the heterogeneity of RIS in Co-containing multicomponent al-loys.These insights could provide the basis for understanding He effects in nuclear materials and open an avenue for tailoring the local chemical order of medium-and high-entropy alloys.

W.T.Lin;G.M.Yeli;G.Wang;J.H.Lin;S.J.Zhao;D.Chen;S.F.Liu;F.L.Meng;Y.R.Li;F.He;Y.Lu;J.J.Kai

Department of Mechanical Engineering,City University of Hong Kong,Hong Kong,China;Institute of Nuclear&New Energy Technology,Tsinghua University,Beijing,China;Department of Physics,Southern University of Science and Technology,Shenzhen,China;Centre for Advanced Nuclear Safety and Sustainable Development,City University of Hong Kong,Hong Kong,China;School of Environmental Science and Engineering,Southern University of Science and Technology,Shenzhen,China;School of Materials Science and Engineering,Shanghai University,Shanghai,China;Nano-Manufacturing Laboratory(NML),City University of Hong Kong Shenzhen Research Institute,Shenzhen,China

材料科学技术（英文版）

[1]W.T.Lin;G.M.Yeli;G.Wang;J.H.Lin;S.J.Zhao;D.Chen;S.F.Liu;F.L.Meng;Y.R.Li;F.He;Y.Lu;J.J.Kai-.He-enhanced heterogeneity of radiation-induced segregation in FeNiCoCr high-entropy alloy)[J].材料科学技术（英文版）,2022(06):226-233

FeNiCoCr

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