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848 |
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Wednesday, June 20, 2007, Brüssel 9:00 AM Fügen von Glas, Keramik und Metall Joining of glass, ceramics, metals |
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Ultrasonic Characterization and Image Analysis of Ag-Cu-Zr Active Braze Joints Between Al2O3 and KovarTM |
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Donald Susan / Sandia National Laboratories, USA Dan Garcia / Sandia National Laboratories, USA Dan Appel/ Sandia National Laboratories, USA Steve Crowder/ Sandia National Laboratories, USA Charles Walker*/ Sandia National Laboratories, USA Joshua Caris/ Sandia National Laboratories, USA |
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Active brazing with Ag-Cu-Zr filler metals is being studied as a method to produce robust ceramic/metal brazements without the need for metallization of the ceramic component. A design of experiments (DOEx) study was performed to assess the process variables involved in active brazing of 94% Al2O3 to Kovar? (low expansion Fe-Ni-Co alloy) to form high-reliability, hermetic joints. Ultrasonic (UT) imaging was used to characterize the joint quality, including porosity content, excess braze flow, and joint underfill. The UT characterization results were confirmed by radiography and metallographic cross-sectioning of the components. The UT images were quantitatively analyzed using color-based image analysis. This technique was useful for determining the relationships between porosity content, lack of hermeticity, and overall joint quality. The UT results were statistically analyzed to determine the main effects variables in the DOEx, which included brazing furnace atmosphere, filler metal washer thickness, and applied load during brazing. Microstructural analysis of the braze joints revealed porosity characteristics as well as the reaction product between the Ag-Cu-Zr active braze and the Al2O3 ceramic. The results of this study were used to develop a more robust brazing process to increase production yields of high-reliability, hermetic braze joints. _____________ Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US Dept. of Energy?s National Nuclear Security Administration under contract DE-AC04-94AL85000. |