Al2O3/Ti interlayer/AISI 304 diffusion bonded joint - Microstructural characterization of the two interfaces

Sintered alumina and AISI 304 stainless-steel discs were joined at 900 degr eesC by solid state diffusion bonding, making use of a Ti foil acting as th ermal stress relief interlayer. The microstructure of the two interfaces th us formed, that is. Al2O3Ti and Ti/AISI 304 was investigated by a variety o f characterization techniques such as scanning and transmission electron mi croscopy (TEM), energy-dispersive X-ray (EDX) microanalysis, X-ray diffract ion and Vickers microhardness, with the Following results: (i) precipitatio n of Ti3Al particles plus Al and oxygen diffusion were detected within the Ti and close to the ceramic: iii) within the Ti foil, coexistence of alpha -Ti and 3-Ti was observed and ascribed to Fe and Cr diffusion and to beta - Ti decomposition during slow cooling from the bonding temperature: and (iii ) adjacent to the Ti/steel interface a 5-mum-thick layer was found to conta in TiFe and Fe2Ti. as well as sigma phase, M23C6 precipitates and TiC. An i nterpretation of these results in terms of element partition during the bon ding process was attempted. (C) 2001 Elsevier Science Inc. All rights reser ved.