The high-conductivity graphite foams are attractive for thermal management applications in avionic heat sinks and heat exchangers. However, integrating foams in thermal systems requires robust and thermally conductive joints between foam and metallic constituents. In this study, graphite foams with different densities were vacuum brazed to titanium using the active braze alloys, Cusil-ABA and Palcusil-5 (in paste and foil forms). The joint microstructure and elemental composition were examined using optical microscopy (OM) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) to evaluate joint integrity, interface microstructure, and chemical interaction. The low-density foams exhibited braze penetration with penetration distance increasing with decreasing bulk density. The carbon/braze interfaces were enriched in Ti indicating sound chemical bonding. The overall thermal resistance of foam/Ti joints was estimated using 1-D, steady-state heat conduction analyses for planar geometries. These calculations indicate a marginal effect of braze saturated foam on joint conductivity for practical range of process parameters.
展开▼
