MICROMECHANISMS OF DYNAMIC FRACTURE OF DUCTILE HIGH-STRENGTH STEEL

Multiscale micromechanisms of dynamic fracture of ductile high-strength Cr-Ni-Mo-V steel are studied by combining a laser interference technique and conventional techniques of optical and electron microscopy. Two scale levels of high-rate strain and fracture were found to form the translational and rotational modes of material motion during shock wave propagation-mesoscopical (0.1-10 mum) and superstructural (50-500 mum). The kinetic and mechanical characteristics of materials at the adjacent scale levels turn out to be in opposite phases relative to each other, strength-characteristics closely connecting with the particle velocity dispersion. Heterogeneous dynamic deformation appears to be realized either in the form of shear bands or in the form of rotational vortices depending on the ratio of particle velocity dispersion and average particle velocity. During dynamic deformation the changing of carbide sizes and lattice parameter occurs, the intensity of these processes being dependent on the mesovolume velocity dispersion as well.