Abstract
The effect of neutron irradiation on the mechanical properties of select molybdenum materials, pure low carbon arc-cast (LCAC) Mo, Mo-0.5% Ti-0.1% Zr (TZM) alloy, and oxide dispersion-strengthened (ODS) Mo alloy, was characterized by analyzing the temperature dependence of mechanical properties. This study assembles the tensile test and analysis data obtained through multiple series of irradiation and post-irradiation experiments. Tensile specimens in stress-relieved conditions with longitudinal (LSR) and transverse (TSR) directions were irradiated in high flux isotope reactor (HFIR) at temperatures ranging 270 to 1100oC to 0.6 -13.1 dpa. Also, the recrystallized LCAC Mo specimens in the longitudinal direction (LR) were also irradiated up to 0.28 dpa at ~80oC. Tensile tests were performed at temperatures ranging from -194 oC to 1400oC. Analysis results indicate that the irradiation at temperatures below 700oC increased strength significantly, up to 170%, while the increase of yield stress by irradiations at higher temperature was not significant. The plastic instability stress was strongly dependent on test temperature but was nearly independent of irradiation dose and temperature. The true fracture stress was dependent on test temperature to a lesser degree than was the yield stress and plastic instability stress. It was also slightly impacted by irradiation, depending on both irradiation and test temperatures. Brittle fracture often occurred in the LSR specimens tested at room temperature or lower after low temperature irradiation, while it was observed in many irradiated TSR specimens over the whole test temperature range. The ODS-LSR specimens showed the highest resistance to irradiation embrittlement due to relatively higher fracture stress. The critical temperature for shear failure (CTSF) was defined and evaluated for the materials, and the CTSF values were compared with the ductile to brittle transition temperatures (DBTT) based on ductility data.
