Title

The Influence of Thermal Cycling on the Properties and Microstructure of Alumina/Kovar Brazed Joints

Authorship

BAGNATO, OSMAR ROBERTO; FERRANTE, MAURIZIO; ZAVAGLIA, CECÍLIA A.C.

BAGNATO, OSMAR ROBERTO

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FERRANTE, MAURIZIO

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ZAVAGLIA, CECÍLIA A.C.

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DOI

10.5151/2594-5327-49v10-55-58

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Abstract

The objective of this paper is to investigate the effect of the thermal cycling and the heat treatment at moderate temperature in the microstructure of metal/ceramic joints. Samples of kovar/alumina were brazed in a vacuum furnace (< 5 × 10⁻⁵ mbar) and vacuum tightness measurements were performed. Samples were heated to 400°C and cooled in air and water (4 and 20°C); other samples were kept at 400°C during 1h and 100h. The results showed that the samples cooled in air did not have cracks and no leakage was detected up to 22 cycles. Analyses by scanning electron microscopy with EDX showed that the microstructure was the same as before one hour of treatment. But after 100h, a continuous film was observed in the interface alumina/filler metal with Ti, Fe, Ni and Co, probably oxides that can impair the mechanical and functional properties.

Keywords

thermal cycling, brazing, alumina, kovar, microstructure