Experimental study and molecular dynamics simulation of Ag/Ti diffusion bonding

Abstract

The diffusion kinetics and mechanisms of Ag/Ti diffusion couple were investigated through experiments and molecular dynamics simulations. The influence of processing parameters, such as temperature (700 °C to 850 °C) and holding time (15 min to 60 min), on microstructure and phase formation at the Ag/Ti joint was studied. In addition, the mechanical properties of the joints were evaluated. IMCs including AgTi, Ti₂Ag, and the Ti(ss, Ag) solid solution exist at the diffusion interface. The activation energy for the growth of the TiAg phase is 98 kJ/mol. Molecular dynamics simulations show that Ag has a higher diffusion coefficient (5.0×10^-5 m²/s) compared to Ti (2.5×10^-8 m²/s). Meanwhile, the grains at the TiAg/Ti interface are significantly smaller than those at the TiAg/Ag side. These results indicate that the diffusion flux of Ag is higher than that of Ti, and the TiAg phase priority is formed at the interface. The grain boundary diffusion is a diffusion control mechanism. The Ti(ss, Ag) solid solution at the interface exhibits the highest nano-hardness and modulus, with values of 4.2 ± 0.1 GPa and 139.6 ± 0.6 GPa, respectively. The joint brazed at 750 °C for 30 min shows a maximum shear strength of 98 MPa, with fractures primarily occurring at the interface between the Ag and TiAg phases. This study provides insights into the diffusion behavior, phase formation dynamics, and mechanical properties of Ag/Ti diffusion couples, offering implications for the development of advanced materials in various engineering applications.