PROCESSING AND PROPERTIES OF MOSI2-NB COMPOSITES

Powder processing techniques for MoSi2 composites are described. The e ffect of Nb morphology on the fracture resistance of the composites wa s studied. Discontinuous random Nb particles or fibers deflected crack s that propagated through the MoSi2 matrix. However, this did not resu lt in any improvements in toughness (as measured from the area under f lexural stress-displacement curves). Aligned Nb fibers oriented perpen dicular to the direction of matrix crack propagation directly particip ated in the fracture of the composite; these fibers toughened MoSi2. H owever, there was an effect of the diameter on the fracture behavior o f the aligned fibers. The effect of fiber diameter on fiber-matrix sep aration could be explained through the load carrying capacity of the f ibers and the ability of the fiber-matrix interface to separate.