Short-Range Order Evolution in Nanocrystalline Mechanically Activated Fe–Cr Alloys in the Process of Annealing

• Published in: Physics of metals and metallography Vol. 121; no. 8; pp. 783 - 790
• Main Authors: Porsev, V. E., Ul’yanov, A. L., Dorofeev, G. A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-08-2020; Springer; Springer Nature B.V
• Subjects: Alloys; Analysis; Annealing; Ball milling; Ball mills; Chemistry and Materials Science; Chromium; Diffraction; Diffusion; Evolution; Ferrous alloys; Grain boundaries; Grain Boundary Segregation; Grain growth; Hyperfine structure; Iron; Material balance; Materials Science; Mechanical alloying; Metallic Materials; Mossbauer spectroscopy; Nanocrystals; Phase separation; Phase Transformations; Segregations; Short range order; Specialty metals industry; Spectrum analysis; Statistical methods; Structure; X-rays; mechanical alloying; phase separation; nanocrystalline Fe–Cr alloys; thermal treatment; short-range order; Mössbauer spectroscopy
• ISSN: 0031-918X; 1555-6190
• DOI: 10.1134/S0031918X20080086

Nanocrystalline Fe–Cr alloys synthesized from pure components in a planetary ball mill with a chromium content of 20–48 at % were annealed for 4 h at temperatures of
T
an
= 400–700°C. Short-range order (SRO) evolution and phase separation dependent on
T
an
were studied using Mössbauer spectroscopy and X-ray diffraction. The precipitation of the σ-FeCr phase was observed only in the samples with 48 at % of Cr at
T
an
 = 600 and 700°C. For all the samples, the grain growth began most intensively from 400°C, and the higher the Cr content in an alloy, the smaller the final size of grains after
T
an
= 700°C. The analysis of behavior of the mean hyperfine field on Fe nuclei and distribution of the hyperfine field width depending on
T
an
, as well as fitting of Mössbauer spectra with spectral components corresponding to the α (Cr depleted) and α' (Cr rich) phases, demonstrated that the mechanically alloyed Fe-Cr samples were characterized by weak short-range separation passing at
T
an
= 400°C to a nearly statistically uniform distribution of atoms. Heterogeneous short-range order with the α and α' regions was formed in the alloys with 30 at % of Cr and more after annealing at 500–700°C. An analysis with the material balance equation led to our conclusion about the existence of the grain boundary segregations of Cr atoms.