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High-Entropy Alloys (HEAs) are an exciting class of materials formed by mixing 5 or more elements and can poses superior high temperature mechanical properties along with excellent irradiation and corrosion resistance. The superior radiation resistance of multicomponent HEAs can be attributed to the sluggish mobility of dislocation loops, formation of fewer voids as well as self-healing capabilities. In particular, HEAs constituted by refractory metals have been proposed as potential structural/functional materials for advanced fission and fusion reactors, primarily because their BCC based structure which offers better resistance to irradiation swelling. However, irradiation of certain BCC- HEAs have also resulted in segregation of atoms like Cr, V, etc at the grain boundaries which can lead to deterioration of mechanical properties. Thus it is necessary to understand the irradiation response of specific alloy compositions in order to explore their suitability for nuclear applications. Study of radiation damage using high energy neutrons can closely mimic advanced reactor conditions, but also pose challenges related to limited availability of high energy neutron sources and handling of irradiated samples due to long term induced radioactivity. On the contrary, proxy ion beam irradiation can act as a better substitute owing to control over ion beam energy, dose rate, irradiation temperature, in addition to shorter irradiation time and comparatively less activation of irradiated specimens. In the present study, the irradiation behaviour of a refractory based 35Nb25Ti25V10Al5Zr (at. %) HEA has been investigated using proton beam at the Low Energy High Intensity Proton Accelerator (LEHIPA) of BARC, Mumbai. LEHIPA consists of a 50 KeV ECR ion source, a 3 MeV radio-frequency quadrupole (RFQ) and a 20 MeV drift-tube Linac (DTL). The 3 MeV beam in the medium energy beam transport (MEBT) section of LEHIPA has been used for the irradiation experiments. Prior to irradiation, the HEA showed a multiphase structure with BCC phase as major and Al-Zr type intermetallic as minor constituents. In LEHIPA, the HEA was exposed to 3 MeV proton beam delivering an average current of ~ 1 µA for 68 h thus imparting a maximum damage of 0.5 dpa. The irradiated alloy was characterized using X- Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Electron back Scattered Diffraction (EBSD), Nano hardness tests and Transmission Electron Microscopy (TEM). Intermetallic content in the HEA was found to reduce significantly after irradiation resulting in the softening of the alloy samples. It is expected that radiation induced order-disorder transformation of the intermetallics is the major reason behind their dissolution into the BCC matrix. The detailed results of the above study will be discussed in this paper.
