期刊
ACTA MATERIALIA
卷 85, 期 -, 页码 199-206出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2014.11.009
关键词
Ni-based superalloys; Cooling rate; Energy-dispersive X-ray spectroscopy; Scanning transmission electron microscopy
资金
- Engineering and Physical Sciences Research Council (United Kingdom) [EP/G035954/1]
- Chinese Scholarship Council
- Defence Treat Reduction Agency [HDTRA1-12-1-0013]
- EPSRC [EP/G035954/1, EP/E020933/1, EP/I005420/1, EP/K005014/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/K005014/1, EP/I005420/1, EP/G035954/1, EP/E020933/1] Funding Source: researchfish
Size-dependent compositional variations under different cooling regimes have been investigated for ordered L1(2)-structured gamma prime (gamma') precipitates in the commercial powder metallurgy Ni-based superalloy RR1000. Using scanning transmission electron microscope imaging combined with absorption-corrected energy-dispersive X-ray spectroscopy, we have discovered large differences in the Al, Ti and Co compositions for gamma' precipitates in the size range 10-300 nm. Our experimental results, coupled with complementary thermodynamic calculations, demonstrate the importance of kinetic factors on precipitate composition in Ni-based superalloys. In particular, these results provide new evidence for the role of elemental diffusion kinetics and aluminium antisite atoms on the low-temperature growth kinetics of fine-scale gamma' precipitates. Our findings have important implications for understanding the microstructure and precipitation behaviour of Ni-based superalloys, suggesting a transition in the mechanism of vacancy-mediated diffusion of Al from intrasublattice exchange at high temperatures to intersublattice antisite-assisted exchange at low temperatures. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd.
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