Compositional effects on mechanical properties of hafnium-carbide-strengthened molybdenum alloys

The mechanical properties of swaged rod thermomechanically processed from arc melted Mo--2Re--Hf--C alloys containing as much as 0.9-mol percent HfC were evaluated. The low-temperature ductilities of these alloys were not influenced by the amount of HfC present but by the amount of Hf in excess of stoichiometry. Maximum ductility occurred at 0.2- to 0.3-at. percent excess Hf. At 0.3- to 0.5-mol percent HfC, alloy strength varied directly with the Mo content of extracted carbide particles, both decreasing as the amount of excess Hf increased. Additions of 2-at. percent Re had little effect on strength or ductility. Tensile and creep strengths of Mo--2Re--0.7Hf--0.5C alloy equaled or exceeded those of other high strength Mo alloys. (auth)