The Role of Stoichiometry on Ordering Phase Transformations in Ni-Cr Alloys for Nuclear Applications

摘要

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.