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.