In the current study, the potential for applying concepts of transient liquid phase sintering (TLPS) to the development of braze filler metals exhibiting variable melting point (VMP) behaviour was investigated.  A Cu-rich Cu and Ni elemental powder mixture was the braze of interest.  The initial melting behaviour, kinetics of isothermal solidification, and the re-melt behaviour of VMP brazes as a function of Cu composition and preparation technique were measured using differential scanning calorimetry  (DSC).  The effects of processing temperature on solid-state sintering and dissolution phenomena were also studied.  The sintered densities of the brazes were also characterized.

It was determined that braze densities above 95% could be achieved with Cu concentrations above 55 vol% or higher.  For a 65 vol% Cu braze, complete isothermal solidification of the liquid at a processing temperature of 1140°C occurred in approximately 90 minutes.    However, solidification of the liquid phase for identical braze mixtures at 1090°C occurred in 45 minutes.  This can be explained by the observed increase in liquid fractions formed at higher processing temperatures (due to the dissolution of Ni), which effectively counteracts the increased diffusion rates at these temperatures and requires more time to isothermally solidify.  The increase in post processing melting point of this braze composition was in excess of 80°C upon reheating.