Modeling copper precipitation hardening and embrittlement in a dilute Fe-0.3at.%Cu alloy under neutron irradiation

Abstract

Neutron irradiation in light water reactors can induce precipitation of nanometer sized Cu clusters in reactor pressure vessel steels. The Cu precipitates impede dislocation gliding, leading to an increase in yield strength (hardening) and an upward shift of ductile-to-brittle transition temperature (embrittlement). In this work, cluster dynamics modeling is used to model the entire Cu precipitation process (nucleation, growth, and coarsening) in a Fe-0.3at.%Cu alloy under neutron irradiation at 300 ̊C. The evolution of the Cu cluster number density and mean radius predicted by the modeling agrees well with experimental data reported in literature for the same alloy under the same irradiation conditions. The predicted precipitation kinetics is used as input for a dispersed barrier hardening model to correlate the microstructural evolution with the radiation hardening and embrittlement in this alloy. The predicted radiation hardening agrees well with the mechanical test results in the literature. Limitations of the model and areas for future improvement are also discussed in this work.

Grizzly and BlackBear: Structural Component Aging Simulation Codes

“…A major part of the Grizzly development effort has focused on developing models to predict the underlying microstructure evolution leading to RPV steel embrittlement, with the goal of developing predictive models for embrittlement over longer-term exposure to the reactor environment. This has involved the development of models at the atomistic scale 11,12 to understand mechanisms of radiation damage to the crystal structure within grains, mean-field cluster dynamics models of precipitation, 13 crystal plasticity models to understand the effects of irradiation on flow stress behavior, 14,15 and cohesive zone model development to model temperature-dependent toughness. 16 Some of these microstructure evolution models are based on continuum theories, while many of them, particularly those that represent behavior at the atomistic scale, are not.…”

Grouping Methods of Cluster Dynamics Model for Precipitation Kinetics

“…To accurately model precipitation behavior, both rates in Equation (2) need to be well determined. The growth rate, also called the "condensation rate" [5,6,[8][9][10], "impingement rate" [1], "capture rate" [2,3,23], or "absorption rate" [4,11,12,[19][20][21], is generally defined from the concentration gradient near a size i cluster surface, as follows [1,5,6,[8][9][10]21,25,26,35]…”

“…The dissolution rate, also called the "emission rate" [1][2][3][4]8,[10][11][12]21] or "evaporation rate" [5,6,9,23], is generally determined using one of two methods. The first method is based on the Gibbs-Thomson equation, which states that the equilibrium concentration near a cluster surface is a function of the cluster size [36], as follows…”

“…When a size i cluster dissolves into a size i − 1 cluster and a single molecule, its volume-related energy stays unchanged, but the interface-related energy increases. The dissolution rate is thus expressed as [1,[3][4][5][6]8]…”

“…Cluster dynamics (CD) is a powerful tool to model microstructure evolution in materials, such as the nucleation, growth and coarsening of precipitates [1][2][3][4][5][6][7][8][9][10][11][12], point defects [13][14][15][16][17][18][19][20], bubbles [21][22][23], or inclusions [24][25][26]. Compared with other models, the CD model has several unique advantages for describing precipitation kinetics, especially in irradiated materials or at an early stage of precipitation.…”