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Molybdenum and its alloys are of interest for applications with extreme thermomechanical requirements such as nuclear energy systems, electronics, aerospace vehicles, and hypersonic vehicles. In the present study, pure molybdenum and samples with added hafnium carbide (HfC) grain refiners were produced using field assisted sintering technology (FAST). The molybdenum and HfC reacted with oxygen to produce MoO2 and HfO2, and increased HfC content from 1 wt% to 5 wt% decreased grain size while the microhardness correspondingly increased. Room temperature three-point bending tests were conducted, and finite element modeling was used to define HfC-dependent bilinear material models. The presence of oxygen most severely affected pure molybdenum, which exhibited little strength and limited ductility, whereas for samples with added HfC, HfO2 was present, resulting in increased toughness hypothesized to be due to microcrack toughening. The samples with 1 wt% added HfC had the greatest energy absorption capability.