THE INFLUENCE OF INTERSTITIAL IMPURITY ON DIFFUSION IN VANADIUM - CR DIFFUSION IN VANADIUM

The influence of an interstitial impurity on the Arrhenius relation of Cr-51 diffusion in vanadium is investigated over a wide temperature r ange. Two types of specimens are used with impurity contents beyond th e quantities usually found in commercial vanadium. Strong curvature si milar to that observed in titanium or zirconium self-diffusion experim ents is observed. It is illustrated that non-linear Arrhenius curves c an be induced by introducing sufficient amounts of interstitial impuri ties such as oxygen. It is concluded that the curvature in refractory b.c.c. metals can be associated either with intrinsic factors or extri nsic effects. The temperature dependence of D in the range of 1420 to 1870 K, obtained by non-linear least squares analysis can be expressed by D(A) = 89.96 exp[-287.12 kJ mol-1)/RT] + 1.0 x 10(-7) exp[-(129.35 kJ mol-1)/RT] cm2/s and D(B) = 89.88 exp[-(257.99 kJ mol-1)/RT] + 1.0 x 10(-7) exp[-(131.8 kJ mol-1)/RT] cm2/s. Calculated diffusivity data of Cr diffusion in vanadium from an earlier work in the temperature r ange 1173 to 1473 K combined with the values of the B specimens of thi s work can be expressed as D = 90 exp[-288.5 kJ mol-1)/RT] + 1.0 x 10( -7) exp[-(157.8 kJ mol-1)/RT] cm2 s-1.