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Crystallography of γ′-Fe4N formation in single-crystalline α-Fe whiskers
- Source :
- Journal of Applied Crystallography. 53:865-879
- Publication Year :
- 2020
- Publisher :
- International Union of Crystallography (IUCr), 2020.
-
Abstract
- Gaseous nitriding of steel and iron can significantly improve their properties, for example corrosion resistance, fatigue endurance and tribological properties. In order to obtain a better understanding of the early stages of formation of the initial cubic primitive γ′-Fe4N, the mechanism and crystallography of the α–γ′ phase transformation was investigated under simplified conditions. Single-crystal α-Fe whiskers were nitrided at 823 K and a nitriding potential of 0.7 atm−1/2for 20 min. The resulting microstructure and phases, as well as the crystallographic orientation of crystallites belonging to a particular phase, were characterized by scanning electron microscopy coupled with electron backscatter diffraction. The habit planes were investigated by single- and two-surface trace analysis. The α-Fe whiskers partly transform into γ′-Fe4N, where γ′ grows mainly in a plate-like morphology. An orientation relationship close to the rational Pitsch orientation relationship and {0.0780.4320.898}αand {0.3910.3670.844}γ′as habit planes were predicted by the phenomenological theory of martensite crystallography (PTMC), adopting a {101}α〈101〉αshear system for lattice invariant strain, which corresponds to a {111}γ′〈112〉γ′shear system in γ′. The encountered orientation relationship and the habit planes exhibit excellent agreement with predictions from the PTMC, although the transformation definitely requires diffusion. The γ′ plates mainly exhibit one single internally untwinned variant. The formation of additional variants due to strain accommodation, as well as the formation of a complex microstructure, was suppressed to a considerable extent by the fewer mechanical constraints imposed on the transforming regions within the iron whiskers as compared to the situation at the surface of bulk samples.
- Subjects :
- 010302 applied physics
Materials science
Scanning electron microscope
Whiskers
02 engineering and technology
021001 nanoscience & nanotechnology
Microstructure
01 natural sciences
General Biochemistry, Genetics and Molecular Biology
Crystallography
Lattice (order)
Martensite
0103 physical sciences
Crystallite
0210 nano-technology
Nitriding
Electron backscatter diffraction
Subjects
Details
- ISSN :
- 16005767
- Volume :
- 53
- Database :
- OpenAIRE
- Journal :
- Journal of Applied Crystallography
- Accession number :
- edsair.doi...........d8add5ab7b214da67ec979bc5337c235