Self-diffusion of V-48 in the FeV σ-phase and in an Fe-47 wt.% V solid solution

Autor: J. Kučera, K. Obrtlík, K. Cíha
Rok vydání: 1982
Předmět:
Zdroj: Czechoslovak Journal of Physics. 32:907-915
ISSN: 1572-9486
0011-4626
DOI: 10.1007/bf01597398
Popis: Self-diffusion coefficients of vanadium in the FeV σ-phase and in the corresponding α-solid solution (Fe-47 wt.% V) measured in the temperature ranges 1002–1115 °C (σ-phase) and 1230–1320 °C are reported. The found results differ fundamentally and significantly from the relations in ordered and disordered solid solutions [9]. The diffusivity in σ-phase at the transition temperature (Tα/σ=1200 °C) is cca 14 times lower than the diffusivity in the b.c.c. solid solution, the chemical composition of which is the same. The lowering is caused by the different values of frequency factors,DOσ=0.11 cm2/s andDOα=45 cm2/s. The effect of the corresponding activation enthalpiesHσ=252 kJ/mole andHα=293 kJ/mole is small and quite opposite. The occurence of higher activation enthalpyHα in the α-solid solution at temperaturesT>Tα/σ may be attributed to a certain amount of the f.c.c. phase coexisting in the b.c.c. matrix at concentrationscv>27 wt.% at sufficiently high temperatures [7]. A comparison of vanadium self-diffusion characteristics measured in the σ-phase to the extrapolated values obtained on the basis of the previous measurements [1] in the Fe-V primary solid solutions α1 shows that the diffusivity ratioDα1/Dσ (1473 K)=33 and that the activation enthalpyHσ is by about 3% higher than the valuesHα1 (eq. (5)) measured in the uniphase b.c.c. solid solutions.
Databáze: OpenAIRE
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