Effects of composition complexity of single-phase concentrated solid solution alloys on He bubbles behavior

Three types of single-phase concentrated solid solution alloys (SP-CSAs) with compositions of NiCoFe, NiCoFeCr and NiCoFeCrMn were prepared using the vacuum arc melting method. The bulk samples were implanted by 100 keV helium ions to a fluence of 5 × 10¹⁶ ions/cm² at 673 K. The transmission electron microscopy (TEM) is employed to systematically characterize helium bubbles along the depth of implantation. The observation results revealed that the He bubble density followed the sequence NiCoFeCr > NiCoFeCrMn > NiCoFe, and the bubble sizes exhibited the trend NiCoFe > NiCoFeCrMn > NiCoFeCr. For NiCoFe and NiCoFeCr, the higher the number complexity of components, the higher the density and the smaller the size of He bubbles. However, the introduction of Mn as a larger-sized atom appeared to increase the vacancy diffusivity and lower the melting temperature, consequently promoting helium bubble growth.