Embrittlement of molybdenum–rhenium welds under low and high temperature neutron irradiation

• Published in: Journal of nuclear materials 2014-01, Vol.444 (1-3), p.404-415
• Main Authors: Krajnikov, A.V., Morito, F., Danylenko, M.I.
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Ductile brittle transition; Ductility; Embrittlement; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Hardening; Installations for energy generation and conversion: thermal and electrical energy; Irradiation; Metals and alloys; Neutron irradiation; Physics; Radiation effects on specific materials; Structure of solids and liquids; crystallography; Transgranular fracture; Welded joints
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2013.10.027

The effect of low- and high-temperature neutron irradiation on the tensile strength, microhardness, and fracture mode has been studied for a series of Mo–Re welds with various Re concentrations. Radiation-induced hardening and concurrent ductility reduction are the key after-effects of neutron exposure. Low-temperature irradiation usually leads to a very hard embrittlement. The hardening effect is rather limited and unstable because of the lack of ductility. Irradiated specimens fail by brittle intergranular or transgranular fracture. The damaging effect of neutrons is less pronounced after high-temperature irradiation. The hardening of the matrix is rather high, but irradiated specimens still keep residual plasticity. High-temperature irradiation intensifies homogeneous nucleation of Re-rich phases, and this effect equalises the difference in mechanical properties between the different weld zones. A characteristic ductility loss exposure temperature was found to separate the temperature fields of absolutely brittle and relatively ductile behaviour. It usually varies between 850K and 1000K depending on the alloy composition and irradiation conditions.