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TLY, the metal/ceramic joints play an important role in many fields of technology and industry. Because of their specific features, they found application as materials that work in hard and changeable conditions. The essence of receiving materials on the basis of metal/ceramic joints is to obtain a strong bond between the metal and ceramic. However, it is difficult, due to the differences in the physical and chemical features between these two types of materials. Therefore, the information concerning wettability, strength, and structure interface of metal/Al2O3 joints plays an important role in the technology of the composite and elements based on the metal/ceramic joints. An important parameter in the processing of metal/ceramic joints is the contact angle of the liquid metal on the ceramic substrate. At equilibrium, the contact angle Q is related to the three interfacial energies: sxy of the solid (s), liquid (l), and vapor (v). This angle is described by the Young equation:[1] cos Qslv ¼ ssv
ssl

[1]

Interfaces between pure metals and ceramics are divided into two classes, i.e., nonreactive and reactive systems. In the nonreactive system, the nature of the ceramic is not significantly modified by its contact with a metal. The wettability is only the result of receiving chemical equilibrium bonds, which are achieved by the mutual saturation of the free valences of the contacting surfaces and acting van der Waals forces. Therefore, the interaction of liquid metal with the ceramic does not form any new phases. In the reactive systems, however, the wetting of the liquid metal on the ceramic occurs intensively together with the chemical reaction and formation of a new solid compound at the metal/ ceramic interface.[2] IWONA SULIMA, Postdoctoral Researcher, is with the Institute of Technology, Pedagogical University, 30-084 Krakow, Poland. BORYS MIKULOWSKI, Professor, is with the Department of Structure and Mechanics of Solid, Faculty of Non-Ferrous Metals, AGH-University of Science and Technology, 30-059 Krakow, Poland. Contact e-mail: [email protected] Manuscript submitted November 4, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A

The Al/Al2O3 system is composed of the two components of the joint, which are important for the production of the metal-matrix composites. Introduction of the Al2O3 particles to aluminum causes an increase of hardness, strength, and abrasion resistance of composites. In the last several years, the development of research concerning the improvement of mechanical properties and wetting in the Al/Al2O3 joints can be observed. This effect can be achieved by the addition of active elements. Many studies were devoted to the effect of metallic coatings on alumina substrate[2–5] and to the effect of different alloying elements[2,6–9] on the structure, wettability, and strength in the Al/Al2O3 system. Alloying additions have a significant effect on the wettability in the Al/Al2O3 joints. Also, alloying can improve or reduce the bond strength between the alumina and metal. The study of the influence of