NSUF 24-4938: Synergetic Effects of Irradiation, Temperature, and Strain on Ordering in Ni-Based Alloys

The objective of this project is to understand how irradiation, thermal aging, and mechanical strain synergistically induce long-range ordering (LRO) in Ni-based nuclear structural alloys. Ni-based alloys are used in existing light water reactors (LWR) owing to their high strength and corrosion resistance and are also planned for advanced reactor structural components because of their molten salt compatibility. In these applications, Ni-based alloys must withstand coupled extreme conditions of thermal aging, irradiation, and mechanical loading. All these stimuli – or combinations thereof – have been shown to cause phase transformations, including the formation of the LRO Ni2Cr phase. However, the role of each of these stimuli in LRO formation, and whether they act synergistically or in competition with one another is not well understood. The presence of these LRO phases leads to hardening, loss of ductility, and compromises corrosion resistance. Thus, there is a critical need to quantitatively understand how the coupled extremes within a nuclear reactor cause long range ordering, so that predictive models can be built to accurately forecast component lifetimes and establish reasonable operating margins. The Taylor-Quinney coefficient (TQC) describes the fraction of mechanical work converted to heat, and can explain similarities between mechanical- and thermal-induced transformations. We hypothesize that irradiation does mechanical work at the atomic level, some fraction of which can be converted to heat, thus resulting in similar mechanical- or thermal-induced phase transformations but with differing kinetics. We will take the approach of conducting synchrotron X-ray diffraction (XRD) to rapidly characterize these LRO phases and their morphologies. Work will consider three alloys spanning a range of Ni:Cr ratios: Alloy 690 (Ni:Cr ~1.8-1.9), Alloy 625 (Ni:Cr ~2.3-2.8), and Alloy 718 (Ni:Cr ~2.5-2.8). For each alloy, we will examine specimens that have undergone combinations of irradiation (I), thermal annealing (T), or mechanical strain (M), specifically I+T+M, I+T, T+M, T only, M only, as well as the baseline as-fabricated materials. Effects of these separate and combined stimuli will be deconvoluted through post-XRD quantification of lattice parameter and Ni2Cr ordering. Ordering ratios between M and T will be related to TQC values; relative “TQC”-like kinetic ratios will then be extrapolated for other conditions.

추가 정보

필드	값
Award Announced Date	2024-05-28T16:55:58.93
Awarded Institution	Purdue University
Facility Tech Lead	Alina Montrose, Simerjeet Gill
Irradiation Facility
PI	Janelle Wharry
PI Email	[email protected]
Project Type	RTE
RTE Number	None