The ϵ → γ′ transformation in N-implanted α-Fe

Abstract

The phase transformations of ϵ-Fe 3− x N to γ′-Fe 4N and γ′-Fe 4N to α-Fe were studied in nitrogen implanted iron. These transformations were studied by the conversion electron Mössbauer spectroscopy (CEMS) technique as a function of time and temperature of annealing of the N-implanted samples. The ϵ phase was formed in the α-Fe sample implanted with 4 × 10 17 N/cm 2 by subsequent 1 hour annealing at temperatures of 200°C, 250°C and 300°C. The samples were then systematically annealed at 300°C, 350°C and 400°C for increasing periods of time in order to follow the decomposition of ϵ and γ′ phases. The detailed analysis of the decomposition rates of these phases allowed the calculation of the activation energies for both transformations as 0.8 eV and 1.3 eV for ϵ → γ′ and γ′ → α transformations, respectively.