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Hardening and Strain Localisation in Helium-Ion-Implanted Tungsten
Suchandrima Das1, Hongbing Yu2, Edmund Tarleton3,4
1Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK. suchandrima.das@eng.ox.ac.uk.
Scientific Reports
|December 5, 2019
Summary
Helium-ion implantation in tungsten (W-3000He) causes initial hardening, followed by softening during deformation. Crystal plasticity finite element modeling successfully simulated nano-indentation, validating this hypothesis.
Area of Science:
- Materials Science
- Nuclear Engineering
- Computational Materials Science
Background:
- Tungsten is crucial for fusion reactor plasma-facing components.
- Neutron irradiation and helium plasma injection cause significant material damage.
- Helium-ion implantation mimics in-service damage effects.
Purpose of the Study:
- To test the hypothesis of helium-induced irradiation hardening followed by softening in tungsten.
- To simulate nano-indentation behavior in helium-implanted tungsten using crystal plasticity finite element modeling.
Main Methods:
- Developed a crystal plasticity finite element (CPFE) model for nano-indentation in helium-implanted tungsten (W-3000He) at 300 K.
- Incorporated thermally-activated dislocation glide through helium-defect obstacles.
- Used defect removal rate as the primary fitting parameter.
Main Results:
- The CPFE model accurately captured the large pile-up observed around nano-indents.
- Simulations predicted localized lattice distortions and geometrically necessary dislocations, quantitatively matching Laue diffraction measurements.
- High-resolution electron microscopy confirmed strain localization beneath nano-indents.
Conclusions:
- The study validates the hypothesis of initial hardening followed by softening in helium-implanted tungsten under deformation.
- CPFE modeling provides a powerful tool for understanding and predicting material behavior in fusion reactor environments.
- The findings contribute to the development of robust plasma-facing materials for future fusion energy applications.
