Simulation of Zr content in TiZrCuNi brazing filler metal for Ti6Al4V alloy

To optimize the Zr content in Ti-based filler metal, the covalent electron on the nearest atoms bond in unit cell ( n A u–v ) with Ti-based BCC structure was calculated, in which the brazing temperature was considered due to its influence on the lattice parameter. Based on EET theory (The Empirical Electron Theory for solid and molecules), n A u - v represents the strength of the unit cell with defined element composition and structure, which reflects the effect from solid solution strengthening on the strength of the unit cell. For Ti–Zr–15Cu–10Ni wt% filler metal, it kept constant as 0.3476 with Zr as 37.5∼45 wt% and decreased to 0.333 with Zr decreasing from 37.5 to 25 wt%. Finally, it increased up to 0.3406 with Zr as 2∼10 wt%. Thus, Ti-based filler metal with Zr content being 2∼10 wt% is suggested based on the simulation results. Moreover, the calculated covalent electron of n A u–v showed good agreement with the hardness of the joint by filler 37.5Zr and 10Zr. The composition of Ti–10Zr–15Cu–10Ni wt% was verified in this study with higher tensile strength of the brazing joint and uniform microstructure of the interface.