Influence of neutron irradiation on Al-6061 alloy produced via ultrasonic additive manufacturing

• Published in: Journal of nuclear materials 2021-07, Vol.550 (C), p.152939, Article 152939
• Main Authors: Gussev, M.N., Sridharan, N., Babu, S.S., Terrani, K.A.
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Aluminum; Aluminum base alloys; Degradation; DIC; Digital imaging; Dimpling; Ductile fracture; Ductility; Fracture mechanics; Fracture surfaces; Heat treating; Heat treatment; Heat treatments; HFIR; Hot isostatic pressing; Image processing; Irradiation; Metallography; Neutron flux; Neutron irradiation; Post-irradiation; Post-weld heat treatment; Radiation; Radiation hardening; Reactors; Recrystallization; Tensile tests; Ultrasonic additive manufacturing; Vibration
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2021.152939

•Specimens of aluminum alloy 6061 produced via ultrasonic additive manufacturing (UAM) were irradiated up to 17.3 dpa.•Post-irradiation evaluation included tensile tests, fractography, and optic microscopy.•X- and Y-specimens, as well as Z-specimens after PWHT/HIP, showed good in-reactor performance. Samples of aluminum alloy 6061 produced via ultrasonic additive manufacturing (UAM) were irradiated in the High Flux Isotope Reactor (HFIR) up to 17.3 dpa at ~70°C while in contact with water using perforated rabbit capsules. The irradiation campaign included as-received (AR) material, specimens subjected to various post-weld heat treatments (PWHTs, including hot isostatic pressing [HIP]), and reference (wrought) alloy samples. Mechanical tensile tests, accompanied by digital image correlation (DIC) analysis, fractography, and metallography, were performed as a part of the post-irradiation evaluation. The X- and Y-specimens (i.e., oriented in the sonotrode moving and vibration directions, respectively) showed pronounced radiation hardening and ductility decrease. Specific serration flow behavior and propagation of deformation bands were observed under various material conditions up to 3.5 dpa but disappeared at 17.3 dpa. In all cases, the fracture mechanism of X- and Y-specimens was ductile; ductile dimples dominated the fracture surface. Irradiated X- and Y-specimens showed good performance, regardless of material conditions (AR or PWHT). The performance of Z-specimens oriented in the build direction was strongly dependent on the PWHT. The AR and aged specimens showed fracture stress decrease with dose, and they experienced fracture under irradiation after 3.5 dpa; specimen cross section analysis revealed specific interface degradation that was likely related to corrosion. Recrystallization significantly improved in-reactor performance. HIP suppressed interface degradation due to recrystallization and pore removal, which led to good in-reactor performance for Z-specimens.