Effects of neutron irradiation on microstructure and deformation behaviourof mono- and polycrystalline molybdenum and its alloys

The influence of neutron irradiation on microstructural evolution and mecha nical properties of mono- and polycrystalline molybdenum and its alloys has been investigated. Tensile specimens and 3 mm diameter discs of monocrysta ls of pure molybdenum and Mo-5%Re were irradiated with fission neutrons at similar to 320 K to displacement doses in the range 5.4 x 10(-4) to 1.6 x 1 0(-1) dpa (NRT) in the DR-3 reactor at Riso National Laboratory. For compar ison, polycrystalline specimens of Mo-5% Re and TZM were also irradiated to gether with the monocrystalline specimens. Both unirradiated and irradiated specimens were tensile tested at 295 K. Post-irradiation microstructures w ere quantitatively characterized using a transmission electron microscope ( TEM). Fracture surfaces were examined in a scanning electron microscope (SE M). The results of tensile testing as well as of transmission and scanning microscopy are presented and discussed in terms of intracascade clustering of self-interstitial atoms and the role of one-dimensional glide of these c lusters in controlling microstructural evolution and the resulting mechanic al properties. (C) 1998 Elsevier Science B.V. All rights reserved.