Effect of irradiation on the mechanical properties of commercially produced Nb₃Sn tapes

Abstract

The effect of neutron irradiation on the mechanical properties of commercially produced Nb₃Sn tapes has been investigated using scanning electron microscopy, sound velocity measurements, tensile and three-point bend tests. The elastic moduli show an increase on irradiation which is independent of dose in the range 4×10²¹ to 4×10²³ neutrons m⁻². The majority of the Nb₃Sn tapes show no evidence of significant amounts of plastic deformation prior to failure, which occurs by the intergranular fracture of the Nb₃Sn layers followed immediately by ductile overload failures of the niobium core. The latter changes to a more brittle failure on irradiation and in tapes containing ZrO₂ particles. The fracture stress decreases for doses up to ∼10²³ neutrons m⁻² but increases at higher doses. Irradiation reduces the critical stress intensity factorK _c, butK _c and the fracture stress are increased in tapes containing ZrO₂. These results are discussed in terms of various micro-structural features and previously determined radiation damage.