| Ceramics have high-temperature strength, good corrosion resistance,high wear-resistance and high electrical isolation. Aluminum has uniqueproperties such as ductility, conductivity, resistance to corrosion, light weight,low permeability to H2and N2. Joining ceramics and aluminum is increasinglyimportant in the production of automobiles, electronic packaging and newceramic armor. However Al oxidized easily, the stable oxides formed on thesurface impede wetting and bonding ceramics to Al.In this paper, Al alloy films were formed on the surface of Al2O3andAlN ceramics by hot-dip aluminizing, and then the ceramics were brazed to Alby adopting conventional brazing methods. The Aluminizing bathcomposition was Al-Si and Al-Cu alloys. To improve the joining of AlNceramic and Al, Fe or Ti were deposited onto AlN ceramic by Magnetronsputtering.Hop-dip aluminizing method can improve wettability of ceramics by Alalloys. Under certain temperature and atmosphere conditions, Al-Si alloyfilms can be formed on Al2O3and AlN ceramics by hop-dip aluminizing andthen Al plates can be brazed tightly on the ceramics by using the films asbraze filler metal. The peel strength exceeds15N/mm. The best brazingtemperature for Al2O3and AlN are625℃to655℃and650℃to655℃,respectfully.During brazing process, Al-Si alloy films become liquid phase, and theliquid phase subsequently solidifies as a consequence of continued diffusionof Si into Al plates. At the end of process, the liquid phase completelysolidifies and a homogeneous metallurgical bond is produced. The bondingmechanism is similar to a transient liquid phase bonding.Increasing Si content in Al-Si alloy films can lower the brazingtemperature and decrease unbounded area. However Si has no direct effect ontear strength of joints. Increasing heating rate can reduce loss of Si and lower brazing temperature.Sputtering Fe on AlN ceramic is harmful for AlN and Al bonding.Sputtering Ti on AlN ceramic can reduce dip-coating temperature, but haslittle effect on brazing. |
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