Transient liquid-phase bonding in the Ni-Al-B system

Transient liquid-phase (TLP) bonding experiments were performed using a Ni-10.3 at, pet Al alloy and a Ni-10 at. pet B filler material, and the results were compared to simulations performed using the finite-difference diffusion code, DICTRA. For the simulations, a thermodynamic assessment of the Ni-Al-B system was used to define the phase diagram and the thermodynamic factors of the diffusion coefficients. Composition-dependent diffusion mobilities were assessed for the ternary system. Predicted liquid widths as functions of time were in good agreement with the experiments. The calculated and experimental Al composition profiles agree in the matrix but not in the liquid. The simulations qualitatively predicted the observed precipitation and later dissolution of the intermetallic tau -phase (Ni20Al3B6) in the base material. This research demonstrated the potential for modeling the formation of spurious phases during TLP bonding of practical superalloy systems.