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Irradiation Hardening in Unalloyed and ODS Molybdenum During Low Dose Neutron Irradiation at 300 Degrees Celsius and 600 Degrees Celsius.

DE2007920290

Publication Date	2007
Personal Author	Cockeram, B. V.; Smith, R. W.; Snead, L. L.
Page Count	64
Abstract	Unalloyed molybdenum and Oxide Dispersion Strengthened (ODS) molybdenum were irradiated at 300DGC and 600DGC in the high flux isotope reactor (HFIR) to neutron fluences of 0.2, 2.1, and 24.3x1024 n/m2 (E>0.1 MeV), producing damage levels of 0.01, 0.1 and 1.3 Mo-dpa. Hardness measurements, electrical resistivity measurements, tensile testing, and Transmission Electron Microscopy (TEM) were used to assess the defect structure. Irradiation hardening was evident even at a damage level of 0.01 dpa resulting in a significant increase in yield stress, decrease in ductility, and elevation of the Ductile-to-Brittle Transition Temperature (DBTT). The observed size and number density of voids and loops as well as the measured irradiation hardening and electrical resistivity were found to increase sub-linearly with fluence over the range of exposure investigated. This supports the idea that the formation of the extended defects that produce irradiation hardening in molybdenum are the result of a nucleation and growth process rather than the formation of sessile defects directly from the displacement damage cascades. The formation of sessile defect clusters in the displacement cascade would be expected to result in a linear fluence dependence for the number density of defects followed by saturation at fluences less than 1-dpa. This conclusion is supported by Molecular Dynamics (MD) simulations of cascade damage which do not reveal large clusters forming directly as a result of the short-term collapse of the cascade.
Keywords	Molybdenum Reactor materials Damage levels Electrical resistivity Yield stress Ductility Neutron irradiation High flux isotope reactor (HFIR) Irradiation hardening Ductile-to-Brittle Transition Temperature (DBTT) Neutron fluences
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Bechtel Bettis, Inc., West Mifflin, PA.; Oak Ridge National Lab., TN.; Department of Energy, Washington, DC.
Supplemental Notes	Prepared in cooperation with Oak Ridge National Lab., TN. Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200810

Irradiation Hardening in Unalloyed and ODS Molybdenum During Low Dose Neutron Irradiation at 300 Degrees Celsius and 600 Degrees Celsius.

Irradiation Hardening in Unalloyed and ODS Molybdenum During Low Dose Neutron Irradiation at 300 Degrees Celsius and 600 Degrees Celsius.
DE2007920290

Publication Date	2007
Personal Author	Cockeram, B. V.; Smith, R. W.; Snead, L. L.
Page Count	64
Abstract	Unalloyed molybdenum and Oxide Dispersion Strengthened (ODS) molybdenum were irradiated at 300DGC and 600DGC in the high flux isotope reactor (HFIR) to neutron fluences of 0.2, 2.1, and 24.3x1024 n/m2 (E>0.1 MeV), producing damage levels of 0.01, 0.1 and 1.3 Mo-dpa. Hardness measurements, electrical resistivity measurements, tensile testing, and Transmission Electron Microscopy (TEM) were used to assess the defect structure. Irradiation hardening was evident even at a damage level of 0.01 dpa resulting in a significant increase in yield stress, decrease in ductility, and elevation of the Ductile-to-Brittle Transition Temperature (DBTT). The observed size and number density of voids and loops as well as the measured irradiation hardening and electrical resistivity were found to increase sub-linearly with fluence over the range of exposure investigated. This supports the idea that the formation of the extended defects that produce irradiation hardening in molybdenum are the result of a nucleation and growth process rather than the formation of sessile defects directly from the displacement damage cascades. The formation of sessile defect clusters in the displacement cascade would be expected to result in a linear fluence dependence for the number density of defects followed by saturation at fluences less than 1-dpa. This conclusion is supported by Molecular Dynamics (MD) simulations of cascade damage which do not reveal large clusters forming directly as a result of the short-term collapse of the cascade.
Keywords	Molybdenum Reactor materials Damage levels Electrical resistivity Yield stress Ductility Neutron irradiation High flux isotope reactor (HFIR) Irradiation hardening Ductile-to-Brittle Transition Temperature (DBTT) Neutron fluences
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Bechtel Bettis, Inc., West Mifflin, PA.; Oak Ridge National Lab., TN.; Department of Energy, Washington, DC.
Supplemental Notes	Prepared in cooperation with Oak Ridge National Lab., TN. Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200810