S. M. Hong, University of California, Berkeley/Lawrence Berkeley National Laboratory, Berkeley, CA; A. M. Glaeser, Berkeley, CA
The mechanical properties and microstructural evolution of metal-ceramic joints produced by transient-liquid-phase (TLP) will be described. Alumina was joined at 773K, 873K, and 973K using a multilayer indium/Cusil-ABA® (commercial copper-silver eutectic brazing alloy)/indium interlayer. The introduction of thin indium cladding layers allows the system to bond at much lower temperatures than those typically used for brazing with Cusil-ABA®, thereby protecting temperature-sensitive components. After chemical equilibriation, the interlayers retain an operating temperature range similar to that of the brazed joints. TLP bonds made at 973K with holding times of 1.5, 6, and 24 h reveal an optimum fracture strength (σ=323.67 ± 29.90) is obtained after 1.5 h. Micrographs of interfaces prepared using single-crystal sapphire reveal disappearance of the liquid phase after 1.5 h at 973K, indicating the possibility of making strong bonds using lower temperatures and/or shorter processing times. Preliminary analysis of the resulting interlayers show that the Ag-In or Cu-In intermetallic phases do not form, and complete dissolution of indium in single-phase silver occurs. The effects of bonding temperature on fracture strength and interlayer microstructures will also be described.
Summary: Metal-ceramic joints produced by transient-liquid-phase (TLP) are studied. Using a multilayer indium/Cusil-ABA/indium interlayer, processing temperatures were effectively reduced from those typically associated with brazing with Cusil-ABA. Mechanical properties and interlayer microstructures will be described.