Melting and solidification of metallic composites in space

Metallic matrix composites are a relatively new type of strengthened metals. Other properties such as wear resistance or thermal and electrical conductivity can also be modified. One can distinguish solid phase and liquid phase fabrication methods. The latter need only a relatively simple equipment and are particularly suited for complex shapes. The interfacial phenomena, the arrangement of the dispersed particles or fibres and the solidification behaviour of the matrix have to be understood in order to enhance the properties of the composite. The microgravity environment of space drastically influences several phenomena occurring during fabrication such as the fluid motion in the liquid matrix and the transport of the solid particles or fibres. The results of our space experiments in SL1, D1, TEXUS 6,7 and 9 on copper and aluminium based composites are summarized in this context. Two topics are treated more in detail, namely the role of interfacial energies and the expulsion of particles by the solidification front. Further, the relevance of space processing is illustrated for oxide dispersion strengthened metals. Finally the constraints of previous experiments and suggestions for future research are mentioned.