Thermal diffusivity recovery and defect annealing kinetics of self-ion implanted tungsten probed by insitu transient grating spectroscopy. (15th June 2022)

• Record Type: Journal Article
• Authors: Reza, Abdallah; He, Guanze; Dennett, Cody A.; Yu, Hongbing; Mizohata, Kenichiro; Hofmann, Felix
• Is Part Of: Acta materialia. Volume 232(2022)
• Publication Date: 2022-06-15
• Subjects: Thermal conductivity -- Point defects -- Fusion materials -- Transient grating spectroscopy -- Annealing -- Defect recovery; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2022.117926
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Tungsten is a promising candidate material for plasma-facing armour components in future fusion reactors. A key concern is irradiation-induced degradation of its normally excellent thermal transport properties. In this comprehensive study, thermal diffusivity degradation in ion-implanted tungsten and its evolution from room temperature (RT) to 1073 K is considered. Five samples were exposed to 20 MeV self-ions at RT to achieve damage levels ranging from 3.2 × 10 −4 to 3.2 displacements per atom (dpa). Transient grating spectroscopy with insitu heating was then used to study thermal diffusivity evolution as a function of temperature. Using a kinetic theory model, an equivalent point defect density is estimated from the measured thermal diffusivity. The results showed a prominent recovery of thermal diffusivity between 450 K and 650 K, which coincides with the onset of mono-vacancy mobility. After 1073 K annealing samples with initial damage of 3.2 × 10 −3 dpa or less recover close to the pristine value of thermal diffusivity. For doses of 3.2 × 10 −2 dpa or higher, on the other hand, a residual reduction in thermal diffusivity remains even after 1073 K annealing. Transmission electron microscopy reveals that this is associated with extended, irradiation-induced dislocation structures that are retained after annealing. A sensitivity analysis shows that thermal diffusivity provides an efficient tool for assessing total defect content in tungsten up to 1000 K. Graphical abstract: Image, graphical abstract