A. K. Ray, A. Kar, S. Mandal, S. Rathod, National Metallurgical Laboratory, Jamshedpur, India
Abstract
Sintered alumina was brazed with 97(Ag40Cu)3Ti active filler alloy at 800, 900, 1000, 1100 and1200O C. 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, 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
Summary: There is no adequate information about the measurement of diffusivity of elements in case of alumina brazing, with active filler alloy from experimental results or data. The measurement of diffusivity across the brazed interface helps understand the nature of reaction takes place during brazing of alumina with active filler alloy, which further promote to produce a good braze joint. Another important aspect of a reliable braze joint is to identify the presence of different phases within the interface, in the present study which has also been taken into consideration and the experimental findings are verified by the help of thermodynamics for it’s further authenticity
