In situ atomic-scale observation of oxidation and decomposition processes in nanocrystalline alloys

• Published in: Nature communications 2018-03, Vol.9 (1), p.946-9, Article 946
• Main Authors: Guo, Jinming, Haberfehlner, Georg, Rosalie, Julian, Li, Lei, Duarte, María Jazmin, Kothleitner, Gerald, Dehm, Gerhard, He, Yunbin, Pippan, Reinhard, Zhang, Zaoli
• Format: Article
• Language: English
• Subjects: 147/137; 147/28; 639/301/1023/1026; 639/301/357/537; Aberration; Alloys; Annealing; Clusters; Consolidation; Contamination; Copper; Copper base alloys; Decomposition; Electron microscopy; Ferrous alloys; Hematite; Humanities and Social Sciences; Iron oxides; Low temperature; Materials science; Metal powders; multidisciplinary; Nanocrystals; Organic chemicals; Oxidation; Oxygen; Plastic deformation; Plastics; Scale (corrosion); Science; Science (multidisciplinary); Solid solutions; Spectrum analysis; Transmission electron microscopy
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-03288-8

Oxygen contamination is a problem which inevitably occurs during severe plastic deformation of metallic powders by exposure to air. Although this contamination can change the morphology and properties of the consolidated materials, there is a lack of detailed information about the behavior of oxygen in nanocrystalline alloys. In this study, aberration-corrected high-resolution transmission electron microscopy and associated techniques are used to investigate the behavior of oxygen during in situ heating of highly strained Cu–Fe alloys. Contrary to expectations, oxide formation occurs prior to the decomposition of the metastable Cu–Fe solid solution. This oxide formation commences at relatively low temperatures, generating nanosized clusters of firstly CuO and later Fe 2 O 3 . The orientation relationship between these clusters and the matrix differs from that observed in conventional steels. These findings provide a direct observation of oxide formation in single-phase Cu–Fe composites and offer a pathway for the design of nanocrystalline materials strengthened by oxide dispersions. Oxygen contamination during the mixing of precursor powders for nanocrystalline materials affects alloy microstructure, but exactly how remains unclear. Here, the authors show that stable nano-oxides can form easily inside severely deformed Cu-Fe grains during heating.