On the partial atomic volume of aluminum in solid solutions based on the 3d transition metals and copper
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NTRODUCTION
ALLOYS based on the 3d transition metals and aluminum are not only important technical and electronic materials,[1] but are also peculiar solids because of the occurence of icosahedral[2,3] and decagonal[4] quasicrystals. An investigation of the affinity between aluminum and the 3d transition metals yields, therefore, useful information which helps to understand the complex interatomic bonding in these binary systems. A reliable method to investigate atomic interactions in solid solutions is the evaluation of the partial atomic volume and the partial molar enthalpy of formation for the solutes.[5] For the binary systems based on aluminum and the 3d transition metals, investigations of the partial atomic volume of aluminum in solid solutions exhibiting the fcc structure (Cu type)[5,6] and the hcp structure (Mg type)[7] were presented previously. The scope of this experimental study is to investigate the partial atomic volume of aluminum in solid solutions with the 3d transition elements showing the bcc structure (W type) and to compare it with the values measured previously for aluminum dissolved in the other quasi-homological transition metals as well as in the 4s1 metal copper. These elements have not only a different d-electronic structure, but also crystal structures of significantly different features such as the coordination number and the space filling. II. EXPERIMENT Metals of the following purity were used for alloy preparation: vanadium (99.99 wt. pct, supplied by Johnson Matthey), chromium (99.999 wt. pct, supplied by Koch–Light), iron (99.99 wt. pct, supplied by Johnson Matthey), and aluminum (99.99 wt. pct, supplied by Heraeus). Metals (approximately 2 g) were melted under argon (Messer–Griesheim 5.0, 40 kPa) in an arc furnace. The weight of the samples was measured before and after alloying; no significant differences were observed. Bulk alloys were enclosed for the M. ELLNER, Senior Research Associate, is with the Max-Planck-Institut fu¨r Metalforschung, D-70569 Stuttgart, Germany. Contact e-mail: m.o. [email protected] I. PARK, former Graduate Student, Dept. of Physical Metallurgy, University of Stuttgart, D-70174 Stuttgart, Germany. Manuscript submitted June 14, 2002. METALLURGICAL AND MATERIALS TRANSACTIONS A
homogenization heat treatment followed by water quenching. The macroscopic density of the alloys was measured at 293 K by the buoyancy method, using CCl4 to check the number of atoms in the solid-solution unit cell. For the powder diffraction investigation, the bulk alloys were filled and sieved (mesh size ⬍ 50 m). Before X-ray diffraction analysis was performed, the fillings were annealed in evacuated small silica tubes to remove residual strain. The homogeneity of the powdered and then heat-treated alloys was checked by means of Guinier patterns (Enraf–Nonius camera FR 552 using Cu K␣1, Co K␣1, and Cr K␣1 radiation). For the unit-cell parameter measurement, Debye–Scherrer patterns (114.8 mm in diameter, capillaries 0.2 mm in diameter, with a single-coated CEA REFLEX 15 film, Stra
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