Non-monotonic behaviour with concentration of the surface tension of certain binary liquid alloys

Abstract

The surface tension σ(c) of most liquid binary alloys usually varies with concentration c in a monotonic way between the values σ₁ and σ₂ of the two pure metals, and this behaviour is well explained by current models. Some alloys show deviations from this ideal behaviour. One of those is Fe–B. The surface tension of this liquid alloy shows a minimum at 17 atomic % B, which corresponds well with the composition of the eutectic point in the phase diagram, followed by a maximum at a concentration of 24 atomic % B or higher. The usual models for the surface tension of liquid binary alloys do not explain those exceptional features, and we propose that a model involving the concentration fluctuations in the liquid alloy has the proper ingredients to account for the features in Fe–B and similar alloys.

Keywords:

• surface tension
• alloys
• liquid metals

Acknowledgements

This work was supported by MCYT of Spain (Grant MAT2005-60544-C03-01) and Junta de Castilla y Leon (Grant VA039A05). N.H.M. wishes to acknowledge the generous hospitality of L.M. Nieto and J.A.A. during visits to the University of Valladolid. N.H.M. was also partially supported at the University of Antwerp by FWO-Vlaanderen project number G.0425.05.