Interfacial Phenomena and Bond Strength in Joining AlN Ceramics Using Metals Foils(Materials, Metallurgy & Weldability)
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The solid state reaction between AlN ceramic and metals foils such as vanadium and titanium was studied between 1323K and 1773K for times ranging from 0.3ks to 72ks. Reaction couples consisting of AlN/Nb and AlN/Ni were also studied. Bonding was carried out in vacuum, in the shape of discs, maintained in contact under a pressure of 7.2mPa. Titanium reacts with AlN at 1323K by forming a thin nitride layer composed of TiN, beside which another reaction layer composed of Ti_3Al existed. The complete diffusion path was observed at 1473K after 7.2ks having a sequence of AlN/TiN/Ti_3AlN/Ti_3Al/Ti. The nitride layer grew slowly with bonding time, on the other hand, the Ti_3Al layer grew following Fick's law with an activation energy of 146kJ/mol. A maximum bond strength of 128MPa was obtained in a joint bonded at 1473K after 28.8ks. The phase reaction in the AlN/V couples started at a temperature of 1573K. Formation of V(Al) and V_2N controls the interface joining of the AlN/V joints. A complete diffusion path could be predicted before 0.9ks at 1573K, following a sequence of AlN/V(Al)/V_2N/V. A maximum bond strength could be obtained for a joint bonded at 1573K after 5.4ks having a structure of AlN/V(Al)/V_2N+V. No ternary compounds could be observed at the AlN/V joining interfaces. Joining AlN using Nb foils requires high temperature (1673K or above). Nb_2Al, Nb_2N, and Nb_3Al_2N were observed at the interface between AlN and Nb. A complete diffusion path was established at 1673K for 7.2ks, having a sequence of AlN/Nb_3Al/Nb_3Al_2N/Nb_2N/Nb. Upon increasing the bonding ttemperature to 1773K, cracks and voids which reduce the bond strength are usually found. A flat interface was observed in the AlN/Ni joints bonded at 1673K after 21.6ks, indicating no formation of compounds except for a trace of Al-Ni solid solution. The bond strength in AlN/Ni couples was poor.
- Transactions of JWRI
Transactions of JWRI 26 (1), 85-91, 1997-07