Channel formation and multiplication in irradiated FCC metals: a 3D dislocation dynamics investigation

Abstract

Our goal in this work is to investigate post-irradiation tensile deformation of FCC grains using 3D dislocation dynamics (DD) simulations. We focus on irradiation dose conditions where plastic strain is expected to localize into defect-depleted channels. Two DD simulation types are used for treating distinct space and time scale effects. Type-I simulations describe the formation of single dislocation channels at a high resolution (nm). Here, the irradiation-induced defects are described explicitly, in the form of prismatic dislocation loops. Type-II simulations are used to describe the channel multiplication process itself, i.e. at the grain scale (μm). This time, the irradiation-induced defects are treated in a simplified way, taking advantage of Type-I simulation results. Simulated channel spacing is found to depend on three main input parameters: the dose-dependent stress level, grain size and critical cross-slip stress. The results are rationalized in terms of a micro-model based on simple, finite-sized dislocation arrangements. The model is further validated by comparison with available experimental evidence.

Keywords:

• dislocation dynamics
• defect structures
• deformation properties
• metallic materials

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. A > 0 and B ensure that k(±l/2) ~ 5.

2. The specific segment motion treatment out of and back to the periodical simulated space makes it irrelevant for channel spacing prediction. It results in unrealistic dislocation microstructures, e.g. unlike those in Figure 3.

3. In austenitic steels irradiated at 300–350 °C, 1021–1022 loops/m³ correspond to 0.25–1.0 dpa, depending on the alloy chemical composition [33].

4. in the acute cross-slip direction, in the obtuse cross-slip direction.

5. The data is for alloy H irradiated to 5.5 dpa at 360 °C, yielding a loop density = 10²³ m⁻³.

Additional information

Funding

This work is financially supported by project PERFORM60 of the Euratom 7th framework program.