Effect of Ti diffusivity on the formation of phases in the interface of alumina-alumina brazed with 97(Ag40Cu)3Ti filler alloy

Abstract

Sintered alumina was brazed with 97(Ag40Cu)3Ti active filler alloy at 1073, 1173, 1273, 1373 and 1473 K. The elemental concentrations along with the thickness of the brazed interface have been measured by the quantitative EPMA line profile analysis. Diffusivity of the elements across the brazed interface is determined using Matano-Boltzmann equation. The diffusivity of Ti, Al, Cu and Ag at different temperature helps in optimizing the brazing process parameter as well as the nature of reaction products formed in the brazed interface. XRD and TEM-EDX analyses confirm the reaction products, such as TiO, Cu3Ti3O. Presence of these phases control the coefficient of thermal expansion mismatches between the substrates and the active filler alloy at the brazed interface. Feasibility of the formation of the phases at the interface has further been verified thermodynamically.