Reactive Potential for the Simulation of Active Brazing of a Ceramic-Metal Interface

Contact between liquid metals and ceramics is common to many manufacturing processes but is difficult to model using molecular dynamics due to chemical complexity, high temperature, and a need for charge transfer during simulations. We present a new seven-element (Fe/Ni/Co/Ag/Al/Zr/O) ReaxFF force-field that has been developed to simulate liquid metal-metal and liquid metal-oxide interfaces, with the goal of modeling the brazing of a metal alloy and alumina. This ReaxFF force-field is specifically intended to accurately describe surface tensions and interfacial reactions that control the reactive wetting process that forms the braze joint and contributes to run-out and underfill defects. Results from simulations with this force-field predict a Zr suboxide layer forming on the alumina-filler metal interface and intermetallic formation at the filler metal-solid metal interface. The ReaxFF force-field has some weaknesses, namely, the high melting point of Ag and the instability of the Ag-alumina interface; however, it shows reasonable heats of formation for a wide range of metal and oxide structures, surface tensions for liquid Ag, and reactions at both the filler metal-Kovar and filler metal-alumina interfaces.