Vanadium diffusion in V–W alloys

• Published in: Physica. B, Condensed matter Vol. 393; no. 1; pp. 259 - 265
• Main Authors: Pelleg, J., Segel, V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30-04-2007; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Diffusion in solids; Diffusion in V–W alloys; Enhancement factor; Exact sciences and technology; Physics; Solute correlation factor; Transport properties of condensed matter (nonelectronic); 66.30.−h; 66.30.Jt; 66.30.Fq; Enhancement factor; Diffusion in V–W alloys; Solute correlation factor; Tracer techniques; Vanadium alloys; Dilute alloys; Diffusion in V-W alloys; Enhancement factor; Solute correlation factor; Diffusion coefficient; Diffusion; Activation energy; Tungsten alloys; Diffusivity; Self-diffusion; 66.30.-h; 66.30.Fq; 66.30.Jt
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2007.01.011

Diffusion coefficients of vanadium in V–W alloys were evaluated by tracer technique at four temperatures in the 1173–1496
K range. No significant changes in the diffusivity of the alloyed specimens in the range of 0–7.1
at% W could be observed beyond the experimental uncertainties. The activation energies are in the range of 357–393
kJ
mol
−1 and the pre-exponential factors are within the limits of 1.8×10
−2–4.4×10
−1
m
2
s
−1.
High concentration W alloys of the V–W system, beyond the commonly accepted 2
at% solute, were used to evaluate the enhancement factors (EF) by applying a linear function for the analysis. At lower temperatures the values of
b, obtained by the linear regression are small and fluctuate in the positive and negative sense ∼0, due to experimental scatter. Le Claire's model, which considers non-perturbing solutes, was applied to estimate the solute correlation factor in the V–W system by assuming that W in V behaves like a non-perturbing solute even at high concentrations. This assumption was based on the similarity between the constituent elements of the V–W alloys.
W diffusion,
D
i
, in pure V is required to estimate
f
i
which enters as
D
i
/
D(0) into Le Claire's relation, where
D(0) is the V self-diffusion coefficient in pure vanadium. This quotient determines the value of
f
i
for certain values of
b. In the absence of W diffusion in V, Mo diffusion in pure vanadium was used in lieu of W to evaluate
D
i
/
D(0). It was found that
f
i
values lie in the range of
f
0<
f
i
<1, but very close to unity,
f
0 being the correlation factor in pure metal.
Diffusion data of W in pure V are required for confirming the assumptions made in this communication. Having such data are also important for the evaluation of the diffusion mechanism. It is also of interest to realize if solutes at high concentration can be used to evaluate
b by a linear function in those cases where solute and solvent resemble each other in their physical properties.