9 - Fabrication processes

Summary

A variety of processes have been and are being developed for the manufacture of MMCs. These may be divided into primary material production, and secondary consolidation or forming operations. A further important distinction can be drawn for the primary processes depending on whether the matrix becomes liquid at any stage. Each technique has its own limitations in terms of component size and shape, and imposes certain microstructural features on the product. Table 9.1 lists the processing routes discussed in this chapter as well as their applicability to the production of the different composite types. In the final section, some observations are made with respect to machining and joining of MMCs.

As can be seen in Table 9.1, many fabrication routes are now available by which a reinforcement can be incorporated into a metal matrix. It is important to note from the outset that making the right choice of fabrication procedure is just as important in terms of the microstructure and performance of a component, as it is for its commercial viability. However, before looking in detail at the various processing options, it is worthwhile dwelling for a moment on selection of the reinforcement. Clearly, the size, shape and strength of the reinforcing particles or fibres is of central importance. Often the choice between the continuous and discontinuous options is relatively straightforward, both in terms of performance and processing cost. However, within each category there exist wide variations in reinforcement size and morphology.