Materials Algorithms Project
Program Library

Program MAP_DATA_SURFACE_TENSION

1. Provenance of code.
2. Purpose of code.
3. Specification.
4. Description of program's operation.
5. References.
6. Parameter descriptions.
7. Error indicators.
8. Accuracy estimate.
9. Any additional information.
10. Example of code
11. Auxiliary routines required.
12. Keywords.
13. Download source code.
14. Links.

Provenance of Source Code

Jeevan Jaidi
Research Scholar,
Mechanical Engineering Department,
Indian Institute of Science,
Bangalore-560012,
INDIA.

E-mail: jaidi@mecheng.iisc.ernet.in

Added to MAP: January 2003.

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Purpose

This code calculates the variation of surface tension and temperature dependence of surface tension (surface tension coefficient) with temperature for the following cases: (a) pure iron and (b) Fe-S binary alloy system, with a given sulfur content.

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Specification

Complete program.

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Description

Surface tension, a thermodynamic property, is function of both temperature and concentration. It measures the strength of the bond between two atoms at the free surface. In general, for pure metals and alloys the bond between two atoms decrease with increase in temperature and result in decreased surface tension. Also, for pure metal and alloys the surface tension coefficient is a constant negative value, always, and is the order of 10^-4 N/m-K. The presence of surface-active elements, such as sulfur, oxygen, selenium, tellurium, etc., strengthen the surface bonds with increasing temperature and result in increased surface tension and hence surface tension coefficient. Further increasing temperature will break the above surface bonds and result in decrease in surface tension and hence surface tension coefficient. The strengthening of the surface bonds is believed to be due to the macro-segregation of surface active elements.

In general, surface tension as a function of temperature and solute activity for a binary alloy system is expressed by the following semi-empirical relation:

The temperature dependence of surface tension (surface tension coefficient) as a function of temperature and solute concentration is given by the follwing expression:

where

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References

1. C. R. Heiple and J. R. Roper, 1982, Welding J., 61, 97s-102s.
2. P. Sahoo, T. Debroy and M. J. McNallan, 1988, Metall. Trans., 19B, 483-491.
3. R. T. C. Choo and J. Szekely, 1991, Welding J., 70, 223s-233s.
4. R. T. C. Choo, J. Szekely and S. A. David, 1992, Metall. Trans., 23B, 371-384.

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Parameters

Input parameters

ACTIVITY_S - real

ACTIVITY_S is the solute activity level (wt%).

CONK1 - real

CONK1 is a constant related to the entropy of segregation.

DELHO - real

DELHO is the standard heat of adsorption (J/mol).

DGAMMADT - real

DGAMMADT is a constant value of surface tension coefficient of pure metal (N/m-K).

GAMMA_S - real

GAMMA_S is the surface excess of the solute species at saturation (mol/m²).

GAMMA_TM - real

GAMMA_TM is the surface tension of pure metal at the melting temperature (N/m).

T - real array

T is the temperature (absolute).

TMELT - real

TMELT is the melting temperature (absolute).

UNICON - real

UNICON is universal gas constant (J/mol-K).

None