Paper number 1270

JOINING MMCS TO METALS

Katarzyna Pietrzak

Institute of Electronic Materials Technology, 133 Wolczynska Str., 01-919 Warsaw, Poland

Summary

Metal matrix composites (MMCs) reinforced with short ceramic fibres (e.g. carbon or Al2O3 fibres) or with other metals (such as e.g., tungsten) show numerous advantages since their properties can be programmed by modifying appropriately their composition and technology. A point of considerable importance is the possibility of joining the composites with metals or their alloys. The major problem here is to choose the appropriate joining technique, such that ensures the formation of a high quality joint resistant to the service conditions, avoids the degradation of the composite micro-structure, in particular of the interface layer between the matrix and the reinforcement, and, still, is not expensive [1]. The paper presents the results of experiments on joining the following composites: CuCr1 - based materials containing 20 vol.% of carbon fibres (Cf), CuZr1 - based materials containing 20 vol.% of carbon fibres (these composites were manufactured by volumetric bonding - the kind of PM method) and Cu - based materials with 10 vol.% of dispersed tungsten powder. The CuCr1-Cf and CuZr1-Cf composites were joined with austenitic steel and CuW composite with copper 99.99% purity. The material pairs were chosen so as to take into account their possible applications. Several different joining techniques were examined. This paper discusses the results obtained when using diffusion bonding and vacuum brazing. The morphology and the nature of the interface layer after bonding process between the matrix and the reinforcement and between the MMCs and metal were examined by analysing the interface distributions of the elements, by SEM and by X-ray techniques. The degree of the degradation of the MMCs structure was taken te be described by the coefficient of the relative content of the reinforcing material RCRM = X/B, where X is the percent content of the reinforcing phase in the composite after the joining process, and B is the percent content of this phase in the starting material. The paper discusses how the nature and morphology of the MMCs to metals joints varies with the joining techniques.

Keywords

carbon fibre-copper composites, joining MMCs, diffusion bonding, active brazing.