CONTROLLED HIGH-RATE LOCALIZED SHEER IN POROUS REACTIVE MEDIA

It is demonstrated that controlled high-strain-rate plastic deformation of heterogeneous reactive porous materials (Nb+Si, Mo+Si+MoSi2) produces shear localization. Within the shear bands, having thicknesses 5-20 μm, the overall strains (γ≤100) and strain rates (γ̇≤10 7 s-1) result in changes in particle morphology, melting, and regions of partial reaction. The shear band thickness is smaller than the initial characteristic particle size of the porous mixture (≤44 μm). This ensures quenching of the deformed material structure in the same time scale as the deformation time (10-5 s). In the shear localization region, two types of patterning are observed: (a) a characteristic shear fracture which subdivides the Nb particles into thin parallel layers and (b) the formation of vortices. © 1994 American Institute of Physics.