The change in tensile properties of wrought LCAC molybdenum irradiated with neutrons

Hardness and electrical resistivity of molybdenum in the post-irradiated and annealed conditions

“…The LCAC molybdenum sheet was obtained from H.C. Starck, Inc. [5]. The chemistry of this material is shown in Table 1 to meet ASTM B386-365 specifications for LCAC [6].…”

“…The LCAC molybdenum was rolled into sheet using standard commercial processing methods, and then given a final stressrelief anneal at 900°C for 1 h [15,16]. A subset of LCAC specimens were recrystallized by heat treatment at 1150°C for 1 h. Subsized SS-1 tensile specimens were machined in the longitudinal or transverse orientation, laser-scribed for identification, pickled in a solution of 10 parts acetic acid + 4 parts nitric acid + 1 part HF acid for 5-15 s to remove 25-51 lm of material, and electropolished [5,15]. Four metallurgical conditions were used for the tensile specimens: (1) longitudinal stress-relieved (LSR), (2) transverse stress-relieved (TSR), (3) longitudinal recrystallized (LR), and (4) transverse recrystallized (TR).…”

“…Molybdenum is a refractory metal with excellent strength and creep-resistance at high temperatures making it of interest for many nuclear and other energy system applications [1][2][3][4][5]. Low carbon arc cast (LCAC) molybdenum is a wrought unalloyed molybdenum form that possesses a high degree of tensile ductility at roomtemperature when the grain size is fine, the carbon content is below 100 ppm, and the carbon to oxygen ratio is high [6][7][8][9][10].…”

“…Low carbon arc cast (LCAC) molybdenum is a wrought unalloyed molybdenum form that possesses a high degree of tensile ductility at roomtemperature when the grain size is fine, the carbon content is below 100 ppm, and the carbon to oxygen ratio is high [6][7][8][9][10]. Neutron irradiation of molybdenum at temperatures <700°C can result in radiation embrittlement that is typically characterized by an increase in the ductile to brittle transition temperature (DBTT), as determined by either tensile testing or bend testing, from below room-temperature to values between 600°C and 700°C following irradiation [1][2][3][4][5]. The radiation embrittlement of molybdenum results from the formation of a high number density of finely spaced point defect clusters, dislocation loops, and/or voids, which limit the homogeneous movement of dislocations and is the result of the slow self-diffusion rate of point defects limiting defect annihilation at irradiation temperatures <700°C.…”

“…The embrittlement of molybdenum at irradiation temperatures <700°C has also been characterized by large increases in hardness and tensile strength [1][2][3][4][5]11]. Electrical resistivity measurements may also be used as an indirect measure of defect density, where larger increases in electrical resistivity are observed following irradiation at lower temperatures due to the presence of a higher number density of defects [12][13][14].…”