Miedema Model and Srikanth Equation for Predicting the Effect of Microalloying Element on the Microstructure of Cu-Ni-Sn Alloy

Abstract

Thermodynamic modeling combining Miedema model, Toop model, and Srikanth equation predicted microalloying effects in Cu-Ni-Sn alloys. Formation enthalpy calculations revealed that Ti, P, Mg, Ca, Zr, Sr, and rare earth element (RE) promoted beneficial intermetallic compound formation with matrix elements, enhancing microstructure and mechanical properties of Cu-Ni-Sn alloys. Activity coefficient analysis showed Ca, Sr, Ba, Zr, and RE additions suppressed Sn segregation by lowering Sn activity. Through detailed analysis of activity coefficient differences between Cu/Ni and Sn components at 673 K, it was demonstrated that the addition of Ti, Zr, La, Ca, Sr, and Ba could significantly retard the nucleation and growth of Cu3Sn and Ni3Sn phases. Among these elements, Ti exhibited the most pronounced retardation effect, followed closely by Zr in terms of their effectiveness in delaying phase formation. These findings provide theoretical guidance for optimizing microalloying strategies in Cu-Ni-Sn alloys.

Keywords: Cu-Ni-Sn alloy, Microalloying element, microstructure, Miedema model, Srikanth equation.