Paper 12.5

Estimation of viscosity for binary and ternary liquid alloys in the Cu-Au-Ag system from thermodynamic data, using a new theoretical approach

 

Kaptay G.1, Zivkovic D.2, Budai I.1

 

1University of Miskolc, Hungary

2University of Belgrade, Bor, Serbia-Montenegro

 

A new theoretical equation is presented for the description of the concentration dependence of viscosity in binary and multi-component liquid alloys. The equation is based on the Eyring equation of viscosity of pure metals. In this new equation, the Eyring equation is modified by taking into account the change in molar volume and cohesion energy during alloy formation, and is written as [1]:

 

 

where   h – Planck constant,

            NAv – the Avogadro number,

            R – universal gas constant,

            T – absolute temperature,

Vi – molar volume of component i,

            DVE – excess molar volume, as function of alloy composition,

            DH – molar heat of mixing, as function of alloy composition,

DGi* - activation energy of viscous flow of pure component i, to be found from the viscosity and molar volume of a pure component from the above equation at  DVE = 0, DH = 0,

0.155 ± 0.015 – a semi-empirical coefficient, obtained from the correlation between the

             cohesion energy in pure liquid metals and the DGi* values, i.e. containing no

             information on any of the binary, or multi-component viscosity data.

 

For using our new equation to estimate viscosity in a given alloy, the following data are needed at a given temperature:

·        viscosity and molar volume values for pure liquid components (metals),

·        the excess molar volume of the alloy (if not available, it can be neglected),

·        the heat of mixing of the liquid alloy.

 

The equation is tested against the known experimental viscosity values in the binary Cu-Ag, Cu-Au and Au-Ag, and also in the ternary Cu-Ag-Au systems (see also [2]). Good agreement between calculated and experimental values is found. The equation can be used to predict viscosity values in other multicomponent systems. 

 

1.      G.Kaptay: Proc. of microCAD 2003 (Metallurgy), University of Miskolc, 2003, pp.23-28

2.      (G.Kaptay: submitted to Metall. Mater. Trans, 2003)

3.      X.M.Zhong, Y.H.Liu, K-C.Chou, X.G.Lu, D.Zivkovic, Z.Zivkovic: J. of Phase Equilibria,

4.      2003, vol.24, No.1, pp.7-11.