Solute and solvent diffusion in V-Zr alloys

Abstract

Solute (95Zr) and solventdiffusion in V-Zr alloys have been studied as a function of solute content (Zr -&2 at.%) and temperature (1578-1883 K for solute diffusion and 1578-1888 K for solvent diffusion). With increasing solute content, diffusion parameters Do and Q for the aolute ("Zr) are found to increese from 8 1 to 2 4 2~ 10-3mm2s-' and 369.2 to 3808kJmol-' respectively, while for solvent (4sV) diffusion they are found to decrease from 11.8 to 5 8 x 10-3m2s-' and 3893 to 3730kJmol-', respectively. Calculations of certain jump frequency ratios and the impurity correlation factorf,, with and without a weak perturbation approximation, agree well for weak solute vacancy interaction. The results are consistent with a vacancy mechanism of diffusion. 9 1. INTRODUCTION Le Claire (1970 a) calculated the enhancement factor for dilute b.c.c. solutions using a weak perturbation approximation (WPA), and later Jones and Le Claire (1972) carried out calculations without this weak perturbation approximation (WWPA). In the present studies of solute and solvent diffusion in V-Zr (Zr-0-2 at.%) dilute alloys, certain jump frequency ratios and the solute correlation factor fi have been calculated using WPA and WWPA in order to assess the effect of partial correlation factors. Q 2. EXPERIMENTAL METHODThe alloys were prepared from nuclear-grade zirconium and 99.95% vanadium. The two metals were mixed in the required proportion and arc-melted in a purified helium atmosphere. The alloys were so prepared to contain 05, 1.0,1.5 and 2-Oat.% of zirconium. The main impurities in the alloys were Fe (400p.p.m) and Si (35 p.p.m.).Samples in the form of rectangular parallelepipeds, 0 8 x 0.8 x 0 3 cm, were cut from the alloy by spark erosion. The end-faces of the samples were made parallel and flat. For grain growth, the samples were heated at 1773 K for 24 hours in vacuum ( Torr); average grain sizes of 2 to 3 mm was obtained. The samples were then polished on carborundum papers of various grades, followed by polishing with diamond paste and alumina (particle size 0.05 pm) on microcloth. Final polishing was with a 3 : 1 mixture of nitric acid and hydrofluoric acid. The polished samples were then thoroughly washed with water and alcohol and stored in acetone.Carrier-free 48V in chloride form and carrier-free 95Zr in oxalate form were obtained from the Radiochemical Centre, Amersham, England, and the Isotope Division of Bhabha Atomic Research Centre, Trombay, respectively. Zircorlium was separated from niobium by the method used by Wacker and Baldin (1950). Thin layers of 48V and "Zr (free from niobium) were deposited on the polished surface of the samples (Agarwala, Murarka and Anand 1968). Downloaded by [University of California Santa Barbara] at 07:38 15 June 2016 28'4 I). I). Pruthi and R. P. AgarwalaFig. 1 0 .o 0.0 2 .o 4.0 6.0 X I O -~ 5 . 0 10.0 xz ("2 1 15.0 x~o -~ Typical penetration plots at 1738 K for 48V diffusing in V-Zr alloys, t =228 x lo4 s (x axis, upper scale) and "Zr diffusing in V-Zr, t = 234 x lo4 s (z axis, lower scale).A...

Calculation of the solvent and solute enhancement factors in BCC metals assuming a hypothetical structure with fourteen first nearest neighbors

“…systems on which we may exercise equation ( 23) dictated the choice of data listed in table 1. The table lists the calculated values of b at the temperatures indicated for the following systems: V diffusion in V/Co [20], Zr diffusion in Zr/V [8], Zr diffusion in Zr/Mn [21] and V diffusion in V/Zr [9] dilute solid solutions, respectively.…”

“…With the obtained data of ω i ω 2 and g p , B eff can be calculated at temperatures for which no experimental values exist. In table 2, B eff values calculated for solute diffusion in the Zr/V [8], V/Co [22], Zr/Mn [21,22] and V/Zr [9] systems are shown. Table 2 also lists the various parameters which were evaluated by fitting to equation (41) of the experimental B values.…”

“…Diffusion enhancement of solvent and solute in dilute alloys by a small impurity concentration has been observed and reported in several communications [1][2][3][4]. The solvent enhancement factor has received wide attention [5][6][7][8][9][10][11], but less consideration has been given to the evaluation of the solute enhancement factor. Theoretical evaluation of these factors for different structures is essential to develop an insight into the diffusion mechanism and to be able to evaluate the meaning of the experimental data.…”