| Shock wave consolidation is an innovative processing technique for the densification of initially porous media. A compressive shock wave is introduced in the material by the impact of a high velocity flyer plate. Densification is achieved via intense inhomogeneous plastic deformation, pore collapse, and localized melting around particle surface. The passage of the shock wave may also induce chemical reactions within the material. The chemical reactivity of the powders are enhanced through dislocation nucleation, plastic flow, grain fracture and mass mixing as a result of the shock wave.; A systematic investigation is performed to examine the effects of particle size and porosity on the initiation of the {dollar}rm Tisb5Sisb3{dollar} reaction from the elemental powder mixture (i.e., 5 Ti + 3 Si). The initial powder porosity is varied from 40% to 49% of the theoretical density for two different size powders. The threshold shock energy necessary for complete silicide reaction is established. The powders are consolidated with shock energies up to 671 J/g and shock pressures up to 7.3 GPa. The threshold shock energy for the large powder mixture is found to be approximately 80% higher than that for the smaller powder mixture. For both sized powders, an increase in the threshold shock energy of 75% is observed in decreasing the initial porosity of the powders from 49% to 40%. Evidence for the reaction of solid Ti and liquid Si is observed in isolated regions at shock energies slightly below the threshold energy.; Mechanical alloying and shock wave consolidation are examined as viable alternatives for the synthesis and consolidation of MoSi{dollar}sb2{dollar}. Mechanical alloying of Mo + 2Si is monitored with X-ray diffraction and differential scanning calorimetry (DSC). The milling time is varied from two hours to one hundred forty-four hours. Nanocrystalline MoSi{dollar}sb2{dollar} is observed after sixteen hours of ball milling. X-ray diffraction is used to follow the extent of alloying and average grain size as a function of ball milling time. DSC is utilized to determine the onset endothermic and exothermic reactions in the ball milled powder. MoSi{dollar}sb2{dollar} is produced from the elemental powder mixture by shock wave consolidation. |
