Defect characterization, mechanical and thermal property evaluation in CVD-W after low-dose neutron irradiation. (December 2019)

• Record Type: Journal Article
• Authors: Yi, Xiaoou; Zhang, Lei; Han, Wentuo; Chen, Jiao; Liu, Pingping; Lv, Yanwei; Song, Jiupeng; Xue, Luwei; Geng, Diancheng; Yoshida, Kenta; Toyama, Takeshi; Zhan, Qian; Wan, Farong; Ohnuki, Somei; Nagai, Yasuyoshi
• Is Part Of: International journal of refractory metals & hard materials. Volume 85(2019)
• Publication Date: 2019-12
• Subjects: CVD-W -- Neutron irradiation -- Defects -- Mechanical properties -- Thermal properties; Heat resistant alloys -- Periodicals; Refractory materials -- Periodicals; Metallography -- Periodicals; Alliages réfractaires -- Périodiques; Matériaux réfractaires -- Périodiques; Métallographie -- Périodiques; Heat resistant alloys; Metallography; Refractory materials; Periodicals; Electronic journals; 669.73
• DOI: 10.1016/j.ijrmhm.2019.105004
• Languages: English
• ISSNs: 0263-4368

Abstract

Abstract: Ultra-high purity (> 99.9999 wt%) chemical vapour deposited tungsten (CVDW) samples were neutron irradiated in the BR2 reactor (Belgium) at Tirr < 210 °C to ~ 0.15 dpa, followed by isochronal annealing at 500, 800 and 1100 °C. Defect characterization showed that dislocation loops dominated the as-irradiated damage microstructure and were mostly ≤5 nm. Void formation was observed after post-irradiation annealing at 1100 °C. The mechanical and thermal properties of CVD-W were evaluated based on tensile tests, Vickers hardness and temperature wave analysis. Fractography study suggested that a transition from intergranular fracture to cleavage fracture took place in the material after neutron irradiation. Hardening was found ~ 23% after irradiation. Subsequent annealing below 800 °C saw further increase in hardness, featuring a maximum value of about Hv = 487. Softening occurred at 1100 °C. Thermal diffusivity dropped by ~ 65% after irradiation and ~ 40% of this degradation recovered at 1100 °C. Highlights: CVD-W coatings were neutron irradiated to 0.15 dpa at Tirr < 210°C, followed by isochronal annealing. Small loops dominated the damage microstructure. Voids were observed after post-irradiation annealing at 1100 °C. Irradiation hardening was found to be ~ 23%. Further increase was found during post-irradiation annealing. A transition of intergranular fracture to cleavage fracture took place in CVD-W after neutron irradiation. Thermal diffusivity degraded by ~ 65% in CVD-W after neutron irradiation.