Processing of alumina-niobium interfaces via liquid-film-assistedjoining Page: 1 of 36
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In press, The Welding Journal
PROCESSING OF ALUMINA-NIOBIUM INTERFACES
JOSEPH T. MCKEOWN, JOSHUA D. SUGAR, RONALD GRONSKY & ANDREAS M. GLAESER
Department of Materials Science & Engineering,
University of California,
Division of Materials Science,
Lawrence Berkeley National Laboratory,
Berkeley, CA 94720
Alumina-niobium interfaces were fabricated at 1400 C via solid-state diffusion brazing of a 127-pm-thick
niobium foil between alumina blocks. Prior to brazing, some of the alumina mating surfaces, both polished
and unpolished, were evaporation-coated with copper films ~1.4 pm, ~3.0 pm, and ~5.5 pm thick to induce
liquid-film-assisted joining at the brazing temperature. The effects of copper film thickness and surface
roughness on fracture characteristics and ceramic-metal interfacial microstructure were investigated by
room-temperature four-point bend tests, optical microscopy, profilometry, and atomic force microscopy.
The average strength of bonds between niobium and polished alumina substrates increased with the
introduction of copper film interlayers, and the scatter in strength tended to decrease, with an optimum
combination of strength and Weibull modulus arising for a copper film thickness of 3.0 pm. The strength
characteristics of niobium bonded to unpolished alumina substrates were also improved by
liquid-film-assisted joining, but were unaffected by the thickness of the copper interlayers.
LBN L Report 55738
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McKeown, Joseph T.; Sugar, Joshua D.; Gronsky, Ronald & Glaeser,Andreas M. Processing of alumina-niobium interfaces via liquid-film-assistedjoining, article, February 15, 2005; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc873254/m1/1/: accessed September 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.