Surface Free Energy of Copper-Based Solid Solutions

Abstract

The surface free energies of “solid–vapor” interfaces and grain boundaries were measured in Cu–Fe solid solutions. The “solid–vapor” interface measurements were performed by the direct “in situ” method in a temperature range from 900 to 1080 °C in a dry hydrogen atmosphere. The solid solutions contained 0.045 at. % Fe, 0.25 at. % Fe, 0.40 at. % Fe, 0.58 at. % Fe, and 0.74 at. % Fe. The grain boundary free energy was obtained by measuring the dihedral angles at the top of the thermal grooves. The isotherms of the surface free energy demonstrated an unusual behavior with a maximum. The surface free energy in Cu-based solid solutions was analyzed. We analyzed both our own and published data. Data were obtained via direct measurements at high (premelting) temperatures. The analysis of Cu–Me systems (Me decreases the surface free energy of copper) showed a strong linear correlation between the logarithm of the surface activity ln(−dFS/dXMe)X→0 and the difference of molar areas of a solute and copper ΔAm (=AmMe – AmCu). Iron-based systems also fit the correlation. The approximating line intersected the difference molar area axis at the positive value.