The Role of Stoichiometry on Ordering Phase Transformations in Ni–Cr Alloys for Nuclear Applications
Mechanical property degradation due to isothermal ageing is of potential concern for alloys based on the Ni–Cr binary system, such as Alloys 625 and 690. The disorder-order phase transformation, which is the primary source of embrittlement, has been studied in Ni–Cr model alloys by experimental approaches. Model alloys with different stoichiometries have been isothermally aged up to 5000 h at three temperatures (373, 418, and 475 °C) and characterized via nano-indentation, atom probe tomography, and transmission electron microscopy. Results show that off-stoichiometry alloys exhibit ordering but at a slower rate than stoichiometric (Ni/Cr = 2.0) alloy.
KeywordsStoichiometry Ordering Ni-based Model alloys
The authors would like to acknowledge funding from the Nuclear Energy University Program (NEUP) of DOE. This material is based upon work supported by the National Science Foundation via the Major Research Instrumentation (MRI) Program under Grant No. 1040588. We also acknowledge the Murdock Charitable Trust and the Oregon Nanoscience and Microtechnologies Institute (ONAMI) for their financial contributions towards the OSU Titan TEM. The authors (Burke and Ciuca) gratefully acknowledge funding from Program EP/N017854/1 from the UK Engineering and Physical Sciences Research Council. The author (Emmanuelle and Li-Jen) would also like to acknowledge technical support from the Michigan Center for Materials Characterization.
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