In-situ TEM/heavy ion irradiation on ultrafine-and nanocrystalline-grained tungsten: Effect of 3 MeV Si, Cu and W ions

• Published in: Materials characterization 2015-01, Vol.99
• Main Authors: El-Atwani, O., School of Materials Engineering, Purdue University, West Lafayette, IN 47907, Birck Nanotechnology Center, West Lafayette, IN 47907, Center of Materials Under Extreme Environments, Purdue University, West Lafayette, IN 47907, Suslova, A., Novakowski, T.J., Hattar, K., Efe, M., Harilal, S.S., Hassanein, A.
• Format: Article
• Language: English
• Subjects: ABSORPTION; ATOMIC DISPLACEMENTS; COPPER IONS; CORRELATIONS; CRYSTALS; DEFECTS; GRAIN SIZE; HEAVY IONS; ION BEAMS; MATERIALS SCIENCE; MEV RANGE 01-10; NANOSTRUCTURES; PHYSICAL RADIATION EFFECTS; RADIATION DOSES; SATURATION; SILICON IONS; SIMULATION; TRANSMISSION ELECTRON MICROSCOPY; TRANSMUTATION; TUNGSTEN; TUNGSTEN IONS
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/J.MATCHAR.2014.11.013

Plasma facing components for future fusion applications will experience helium- and neutron-induced structural damage. Direct observation of the in-situ dynamic response of such components during particle beam exposure assists in fundamental understanding of the physical phenomena that give rise to their irradiation resistance. We investigated the response of ultrafine and nanocrystalline-grained tungsten to 3 MeV heavy ion irradiations (Si{sup 2} {sup +}, Cu{sup 3} {sup +} and W{sup 4} {sup +}) for the simulation of neutron-induced damage through transmutation reactions via in-situ ion irradiation–transmission electron microscopy experiments. Defect densities as a function of irradiation dose (displacement per atom) and fluence were studied. Four stages of defect densities evolution were observed, as a function of irradiation dose: 1) increase in defect density at lower doses, 2) higher defect production rate at the intermediate doses (before saturation), 3) reaching the maximum value, and 4) drop of the defect density in the case of W{sup 4} {sup +}, possibly due to defect coalescence and grain boundary absorption of small defect clusters. The effect of grain size on defect densities was investigated and found that defect densities were independent of grain size in the ultrafine and nanocrystalline region (60–400 nm). These results were compared to other heavy ion irradiation studies of structural materials. - Graphical abstract: Bright-field TEM micrographs and defect densities of UF and NC tungsten grains irradiated with a) Si{sup +} {sup 2} at 1.03 dpa: 1) 140 nm — 7.2 × 10{sup −} {sup 3} defects/nm{sup 2}, 2) 122 nm — 6.9 × 10{sup −} {sup 3} defects/nm{sup 2}, 3) 63 nm — 4.7 × 10{sup −} {sup 3} defects/nm{sup 2}, and 4) 367 nm — 6.4 × 10{sup −} {sup 3} defects/nm{sup 2}; b) Cu{sup +} {sup 3} to 3.79 dpa: 1) 228 nm — 4.3 × 10{sup −} {sup 3} defects/nm{sup 2}; 2) 202 nm — 5.9 × 10{sup −} {sup 3} defects/nm{sup 2}; and 3) 137 nm — 6.1 × 10{sup −} {sup 3} defects/nm{sup 2}; and c) W{sup +} {sup 4} to 5.72 dpa: 1) 372 nm — 2.3 × 10{sup −} {sup 3} defects/nm{sup 2} and 2) 128 nm — 4.5 × 10{sup −} {sup 3} defects/nm{sup 2}. - Highlights: • Heavy ion irradiations were performed on UF and NC grained tungsten. • Irradiations were performed with 3 MeV (Si{sup 2} {sup +}, Cu{sup 3} {sup +} and W{sup 4} {sup +}) ions at RT. • Defect density vs. dpa demonstrated four different stages in the case of W{sup 4} {sup +} irradiation. • Defect coalescence and absorption