Atomic resolution characterization of strengthening nanoparticles in a new high-temperature-capable 43Fe-25Ni-22.5Cr austenitic stainless steel

0491758 - ÚFM 2019 RIV CH eng J - Journal Article
Heczko, Milan - Esser, B.D. - Smith, T. M. - Beran, Přemysl - Mazánová, Veronika - McComb, D. W. - Kruml, Tomáš - Polák, Jaroslav - Mills, M. J.
Atomic resolution characterization of strengthening nanoparticles in a new high-temperature-capable 43Fe-25Ni-22.5Cr austenitic stainless steel.
Materials Science and Engineering A Structural Materials Properties Microstructure and Processing. Roč. 719, MAR (2018), s. 49-60. ISSN 0921-5093. E-ISSN 1873-4936
R&D Projects: GA MŠMT(CZ) LQ1601; GA ČR(CZ) GA13-23652S; GA MŠMT LM2015069
Institutional support: RVO:68081723 ; RVO:61389005
Keywords : Scanning transmission electron microscopy * Austenitic stainless steel * High temperature * Fatigue * Strength * Nanoparticles
OECD category: Audio engineering, reliability analysis; Audio engineering, reliability analysis (UJF-V)
Impact factor: 4.081, year: 2018

Advanced scanning transmission electron microscopy (STEM) was used to study two distinct populations of nanoparticles associated with the extraordinary strengthening of the highly-alloyed austenitic stainless steel Sanicro 25 during cyclic loading at 700 degrees C. Fully coherent and homogeneously dispersed Cu-rich nanoparticles precipitate rapidly as a result of thermal exposure, along with nanometer-sized incoherent NbC carbides that nucleate on dislocations during the cyclic loading at high temperature. The atomic structure of nanoparticles was investigated by probe-corrected high-angle annular dark-field STEM imaging. Compositional analysis of the nanoparticles was conducted using high spatial resolution energy dispersive X-ray spectroscopy combined with electron energy-loss spectroscopy. Experimental observations were validated by image simulations of the Moire-like contrast exhibited by NbC carbides. The important role of both nanoparticle populations for the overall cyclic response is discussed. As a result of pinning effects and associated obstacles, dislocation motion is significantly retarded preventing formation of substructures with lower stored internal energy. With recovery heavily suppressed, forest dislocation strengthening supported by precipitation and solid solution hardening, leads to the remarkable increase of cyclic strength at elevated temperatures.
Permanent Link: http://hdl.handle.net/11104/0286807