Phase-decomposition-related short-range ordering in a Fe-Cr alloy

TL;DR

This study investigates how phase decomposition affects short-range atomic ordering in a Fe-Cr alloy during annealing, using Mössbauer spectroscopy to analyze atomic configurations and their evolution over time.

Contribution

It introduces a detailed analysis of atomic configurations and SRO parameters during phase decomposition in Fe-Cr alloys, linking experimental data with theoretical models.

Findings

SRO parameters follow Johnson-Mehl-Avrami-Kolgomorov kinetics.

Linear correlation between SRO and hyperfine field.

Evidence supporting nucleation and growth mechanisms.

Abstract

A redistribution of Cr atoms related to a phase decomposition (PD) caused by an isothermal annealing at 415 C in a 15.15 at%Cr Fe-Cr alloy was studied in an ex-situ way by the conversion electrons M\"ossbauer spectroscopy. Analysis of the spectra in terms of a two-shell model enabled determination of probabilities of 17 different atomic configurations and average numbers of Cr atoms within the first (1NN) and the second (2NN) neighbor shells versus annealing time, separately. The annealing-time evolution of these numbers, expressed in terms of the Cowley-Warren short-range order (SRO) parameters, was shown to follow the Johnson-Mehl-Avrami-Kolgomorov equation. The SRO-parameter averaged over the 1NN-2NN shells was revealed to be linearly correlated with the average hyperfine field. Signatures in favor of the nucleation and growth mechanisms responsible for PD are discussed, too.