THE DIFFUSIVITY AND SOLUBILITY OF NITROGENnIN MOLYBDENUM AND THE TRAPPING OF NITROGEN BY CARBON IN MOLYBDENUM

摘要

By employing ultra-high vacuum techniques, the outgassing kinetics of nitrogen-saturated molybdenum have been determined over a wide range of temperatures (1050-1925℃) and satura¬tion pressures (0-760 Torr) using both single and polycrystalline samples con¬taining various amounts of carbon (< 2-430 wt ppm). It was found that the degassing rate is strictly diffusion-controlled under all conditions studied, thus allowing the diffusivity and the solu¬bility of N in Mo to be calculated from the kinetic data.nPronounced trapping effects have been observed when C is present in amounts exceeding the solubility limit. Trapping is manifest by:(1) anomolously low values of the diffusion coefficient, together with a significantly higher activation energy for N diffusion;and (2) high apparent values of the solubility. When C is all in solution instead of in second-phase pre¬cipitates, both the diffusivity and solubility of N are the same as for C-free samples.