EFFECTS OF OXYGEN, NITROGEN AND CARBON ADDITIONS ON THE MECHANICAL-PROPERTIES OF VANADIUM AND V-MO ALLOYS

Effects of oxygen, nitrogen and carbon additions on the mechanical properties at room temperature of vanadium and V-Mo alloys containing up to 25 at% molybdenum were studied. The V-O, N or C and V-Mo-O, N or C alloy systems, respectively, were prepared by heating vanadium and the V-Mo alloys with oxygen, nitrogen or propane gas in sealed quartz capsules. The prepared alloys were homogenized, argon-quenched and analyzed for oxygen, nitrogen and carbon content. Then they were examined by tensile and hardness tests at room temperature, SEM observations and TEM studies. Oxygen and nitrogen additions to vanadium and the V-Mo alloys raise the hardness by solid solution, with nitrogen being more effective. Carbon additions to vanadium form coarse precipatates of V2C along the grain boundaries, which do not raise the hardness, while those to the V-Mo alloys form fine precipitates of vanadium carbide, homogeneously distributed in the matrix, which raise the hardness. Threshold concentrations of oxygen, nitrogen and carbon for embrittlement (fracture without plastic deformation) of these alloy systems decrease with increasing molybdenum concentration, those of carbon being most detrimental. Also, it was shown that the embrittlement of the V-Mo alloys after exposure to liquid sodium may be explained not only by solid solution hardening due to absorbed oxygen but also by combined effects of absorbed oxygen, nitrogen and carbon. © 1979.