Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

Shenyan Huang, Yanfei Gao, Ke An, Lili Zheng, Wei Wu, Zhenke Teng, Peter K. Liaw

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65 Scopus citations

Abstract

The ferritic superalloy Fe-10Ni-6.5Al-10Cr-3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.

Original languageEnglish
Pages (from-to)137-148
Number of pages12
JournalActa Materialia
Volume83
DOIs
StatePublished - Jan 15 2015

Funding

This work was supported by the U.S. Department of Energy (DOE), Office of Fossil Energy, under Grants DE-FG26-09NT0008089 and DE-FE0005868 , with Vito Cedro and Richard Dunst as program managers, respectively (S.Y.H., W.W., Z.K.T. and P.K.L.), by the National Science Foundation CMMI 0800168 (L.L.Z.), and by the Center for Defect Physics, an Energy Frontier Research Center funded by the DOE Office of Science, Basic Energy Sciences (Y.F.G.). A portion of this research at the Spallation Neutron Source, Oak Ridge National Laboratory, was sponsored by the Scientific User Facilities Division of the DOE Office of Science, Basic Energy Sciences. The authors thank Ms. Rebecca Mills, Mr. Harley Skorpenske and Mr. Michael Rawlings for their experimental assistance.

Keywords

  • Ferritic superalloy
  • High-temperature deformation behavior
  • Neutron diffraction

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