CERAMIC JOINING-II PARTIAL TRANSIENT LIQUID-PHASE BONDING OF ALUMINA VIA CU/NI-CU MULTILAYER INTERLAYERS

Multilayer Cu/Ni/Cu interlayers that form a thin layer of a Cu-rich transient liquid phase have been used to join alumina to alumina at 1150-degrees-C. The method and bonding conditions yield an assembly bonded by a Ni-rich (>94 at% Ni) interlayer at a temperature substantially lower than those normally required for solid-state diffusion bonding with pure Ni interlayers. Flexure strengths of as-bonded beams ranged from 61 to 267 MPa with an average of 160 MPa and a standard deviation of +/-63 MPa. The highest flexure strengths were observed in samples where failure occurred in the ceramic. Post-bonding anneals of 10 h duration in air and gettered-argon at 1000-degrees-C decreased the average room temperature strength to 138 and 74 MPa, respectively. In as-processed and annealed samples, varying degrees of interfacial spinel formation are indicated. Spinel formation may contribute to the scatter in as-processed samples, and the decrease in strength values resulting from annealing.