The effect of an interstitial impurity upon the Arrhenius relationship for 51Cr diffusion was investigated, over a wide temperature range, by using 2 types of specimen. Both types had impurity contents which were above those usually found in the commercial material. A marked curvature, which was similar to that observed in the case of Ti and Zr self-diffusion, was observed. It was shown that non-linear Arrhenius curves could be produced by introducing sufficient amounts of an interstitial impurity such as O. It was concluded that the curvature in refractory body-centered cubic metals was associated with intrinsic or extrinsic effects. The temperature dependences of Cr diffusivity in the 2 types of material, at temperatures ranging from 1420 to 1870K, could be described by:

D (cm2/s) = 89.96 exp[-287.12(kJ/mol)/RT] + 1.0 x 10-7exp[-129.35(kJ/mol)/RT]

and

D (cm2/s) = 89.88 exp[-257.99(kJ/mol)/RT] + 1.0 x 10-7exp[-131.9(kJ/mol)/RT]

By combining the latter data with earlier results, for temperatures ranging from 1173 to 1473K, the expression:

D (cm2/s) = 90 exp[-288.5(kJ/mol)/RT] + 1.0 x 10-7exp[-157.8(kJ/mol)/RT]

was obtained.

J.Pelleg: Physica Status Solidi A, 1995, 147[2], 361-71

Table 309

Diffusivity of 51Cr in V