Journal
ACTA MATERIALIA
Volume 81, Issue -, Pages 487-500Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2014.08.054
Keywords
Nano-twinned structures; Austenitic steels; Plastic deformation mechanism; TEM and EBSD characterization
Funding
- Ministry of Science and Technology of China [2012CB932201]
- National Natural Science Foundation [51371172, 51231006]
- German Research Foundation (Deutsche Forschungsgemeinschaft DFG) [SFB-761]
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A novel type of duplex microstructure is generated in a single-phase austenitic steel (AISI 316L; X2CrNiMo19-12), consisting of plastically compliant recrystallized austenitic grains as the matrix containing coarse non-recrystallized grains with a nanotwinned austenitic (nt-gamma) structure as strengthening inclusions. This novel type of single-phase yet duplex microstructured steel exhibits an excellent combination of strength and ductility. We study the plastic co-deformation mechanisms between the nanotwinned and the recrystallized grains under tension using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). At tensile strains below 5%, the nt-gamma grains nearly deform homogeneously in conjunction with the surrounding statically recrystallized (SRX) grains without generating notable strain localization near their interfaces. The anisotropic plastic deformation of the nt-gamma grains with predominant shear parallel to the twin boundaries results in a higher dislocation density in the neighboring SRX grains. As the strain exceeds 12%, localized deformation occurs within the nt-gamma grains in the form of shear banding. A strain gradient is developed in the surrounding SRX grains as a function of distance from the nt-gamma/SRX interface. Deformation twinning is observed in the SRX grains near the nt-gamma grains, while away from nt-gamma grains dislocation slip dominates the deformation. The strengthening effect of the strong and ductile nt-gamma grains may offer a novel approach to strengthen austenitic steels and related alloys by generating a nanotwinned/recrystallized duplex microstructure. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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