A relation between the hyperfine magnetic and electronic structure and the passivability of the heat treated Fe-23% Cr alloy

Abstract

The effect of heat treatment conditions (quenching and tempering at 475°C for 200 h or at 650°C for 10 h) on the hyperfine magnetic structure, electron density distribution at 57Fe nuclei, and passivability of Fe-23% Cr alloys in either a highly pure state or with a heightened content of impurity elements is studied with the use of Mössbauer γ-resonance spectroscopy combined with voltammetric measurements in a 1 mol/l HClO4 + 0.25 mol/l NaCl solution at room temperature. Mössbauer spectra are processed (decomposed in three subspectra) with the help of Normos computer program, and the following parameters are estimated: the effective magnetic field intensity H eff (kOe); the half-width of the first subspectrum peak Γ (mm/s); the first-to-third (W 13) and second-to-third (W 23) ratios of the subspectrum peaks; the isomeric (chemical) shift δ (mm/s) with respect to α-Fe; the quadrupole electric splitting Δeq (mm/s); and the area part S (%) of the hyperfine structure subspectrum in the summary spectrum. Hyperfine magnetic structure and electron density distribution at iron nuclei are found to change depending on the alloy purity and heat-treatment conditions. The γ-spectroscopy data are considered in relation to the passivating characteristics of the alloy.