PROCESSING AND PROPERTIES OF NB5SI3 AND TOUGH NB5SI3 NB LAMINATES

Both mechanical alloying (MA) and reactive sintering (RS) techniques were successfully used to produce Nb5Si3. The homogeneity of the mechanically prealloyed powders and that of the Nb-Si powder blend before RS significantly affected the microstructures produced after hot-press consolidation. Model laminates of mechanically alloyed Nb5Si3 and nominally pure niobium were prepared via vacuum hot pressing. Room temperature toughness tests were conducted inside a scanning electron microscope equipped with a deformation stage to evaluate the effect of the niobium reinforcement on the composite fracture behavior. Significant toughness increases were obtained in the laminates, while the niobium exhibited both cleavage and ductile fracture. These results are discussed in light of recent work on ductile phase toughening of brittle materials. It is also shown that the RS process may offer an alternative approach, other than in situ and arc melting and casting processes, for producing both monolithic and ductile-phase reinforced Nb5Si3.