Effect of He-ions irradiation on the microstructure and mechanical properties of TiTaNbZr refractory medium-entropy alloy film

Abstract

In this work, TiTaNbZr refractory medium-entropy alloy (RMEA) films were irradiated by 60 keV helium (He) ions at the fluence of 5 × 1016 cm−2 - 2 × 1017 cm−2. After irradiation, a structural transformation of amorphous-BCC single phase, namely self-healing behavior, in TiTaNbZr RMEA films was revealed on account of the enhanced diffusion and redistribution of atoms, which could also lead to a decrease of defects. In this process, increased grain boundaries, acting as effective defect sinks, have inhibited the He bubbles within crystals. The short-range migration of atoms did not destroy the uniformity of elements dramatically. In addition, the correlation between the structural transformation and mechanical properties evolution in the RMEA films was also further clarified. No degradation of mechanical properties even for irradiation fluence as high as 2 × 1017 cm−2 due to the increased grain boundaries and self-healing mechanism. These results all indicate that the TiTaNbZr RMEA have outstanding irradiation resistance and potential applications in reactor structural materials. Meanwhile, the microstructural transformation and performance evolution of the TiTaNbZr RMEA explored in this study could provide more understanding of irradiation effect and a new perspective for the development of the alloys with self-healing ability in refractory high/medium entropy alloys (RHEAs/MEAs).