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

卷:719

Article

Heczko, M.^1,2  Esser, B. D.¹  Smith, T. M.³  Beran, P.⁴  Mazanova, V.²  McComb, D. W.¹  Kruml, T.²  Polak, J.²  Mills, M. J.¹ 

[1] Ohio State Univ, Dept Mat Sci & Engn, Ctr Electron Microscopy & Anal, 1305 Kinnear Rd, Columbus, OH 43212 USA

[2] ASCR, Inst Phys Mat, Zizkova 22, Brno 61662, Czech Republic

[3] NASA, Glenn Res Ctr, 21000 Brookpk Rd, Cleveland, OH 44135 USA

[4] ASCR, Nucl Phys Inst, Rez Near Prague 25068, Czech Republic

关键词: Scanning transmission electron microscopy;    Austenitic stainless steel;    High temperature;    Fatigue;    Strength;    Nanoparticles;   

DOI  :  10.1016/j.msea.2018.02.004

来源: Elsevier

【 摘 要 】

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.

【 授权许可】

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