Study of vacancies in Fex(CoCrMnNi)100-x medium- and high-entropy alloys by positron annihilation spectroscopy

Abstract A study of vacancies in Fex(CoCrMnNi)100-x medium- and high-entropy alloys by positron annihilation spectroscopy (PAS) was carried out. Positron lifetime studies showed that specimens of Fex(CoCrMnNi)100-x alloys (x = 20, 40, 50, 60) contain monovacancies characterized by positron lifetime of ≈170 ps. The alloys with a composition closer to equimolar, i.e. with lower Fe content, exhibited higher configurational entropy and a lower concentration of monovacancies. This was related to the dependence of the vacancy formation enthalpy on Fe content in the Fex(CoCrMnNi)100-x system. Coincidence Doppler broadening revealed that Mn content is enhanced in the vicinity of vacancies.