Joints of high-purity Al2O3 were made with a Ag57Cu38Ti5 alloy by vacu
um brazing at 800 degrees C and 900 degrees C for 30 min. The microstr
uctures at the interface between the ceramic and the alloy were examin
ed in cross-section by scanning electron microscope (SEM) and on diffe
rent planes parallel to the interface layer-by-layer by optical micros
cope (OM), respectively. The chemical composition of the reaction prod
uct was also analysed by energy dispersive X-ray (EDX). A thin reactio
n layer about 1.0 mu m thick was formed on the Al2O3 surface at a temp
erature of 800 degrees C. This layer had th ree kinds of morphologies
and they were identified as Ag, Cu2Ti4O and AlTi, respectively. Accord
ing to SEM and OM results, there were two distinct layers 4.0 mu m thi
ck interfacial reaction layer for sample heated at 900 degrees C, one
layer in the vicinity of the ceramic consisting mainly of Ti2O and TiO
and the other layer near the alloy was CuTi2. A transition layer stru
cture composed of Al2O3/Ti2O + TiO/Ti2O + TiO + CuTi2/CuTi2/Ag-Cu was
formed at the interface. The Al concentration at the interface was rel
atively high and confirmed that the reduction of Al2O3 by Ti occurred,
which was consistent with the result of a thermodynamic analysis.