Effect of rare earth elements scandium on Sn-0.7Cu brazing metal: First-principles calculation

Abstract

In this paper, the effects of rare earth element Sc on the thermal and mechanical properties of precipitates (Cu6Sn5), (Cu3Sn) and Sn matrix in Sn-0.7Cu brazing metal, as well as the interface bonding strength between stable precipitates (Cu6Sn5) and Sn matrix were investigated based on first-principles calculations. The results show that the electronic structure of the precipitated phase and the matrix changes to a certain extent, the atomic bonding mode recombines, and the electron orbitals of the matrix atoms and the rare earth elements hybridize. In addition, rare earth elements improve the mechanical properties of precipitated phase and matrix, increase the plasticity of precipitated phase and enhance the strength of matrix. Rare-earth elements improve the thermodynamic properties of the matrix and precipitated phase to some extent, increase the heat capacity of the precipitated phase and the matrix, and reduce the melting point. At the same time, rare earth elements enhance the mechanical properties and thermodynamic stability of the interface between the precipitated phase and the matrix, and improve the oxidation resistance of the matrix. Transmission electron microscope (TEM) observation shows that there is a segregation of Cu atoms at the interface between precipitated phase and matrix. Other experimental results show that: Rare-earth element Sc has a positive effect on the mechanical properties, melting characteristics and oxidation resistance of the filler metal alloy. When the addition of Sc is 0.1 % (wt), the tensile strength and elongation of the alloy are significantly increased, the melting point is reduced, the surface oxidation resistance is increased, and the comprehensive properties of the alloy are the best.