Volosyuk М. Relaxation of mechanical stress in crystalline solids with FCC lattice (Cu, KCl, NaCl) near stress concentrators

The investigation results on formation of a contact area between copper (99.999 %) polycrystalline samples clamped together at 0.8Tm are presented. The new mechanism of the final stage of the process is proposed where in the contact plane a system of cavities occurs and vacancy supersaturation takes place; as a result, dislocation loops are dissolved and the flow of atoms occupies the cavities. These are healed, so the contact area increases. Both the dislocation and the dislocation-diffusion mass-transfer mechanisms are generalized for the crack healing under uniaxial loading at room and higher (>0.5Тm) temperatures. The theoretical models proposed and the process valuations have been supported experimentally. Formation of cavities in KCl single crystals has been studied under action of focused pulse laser radiation. It was established that (96-98)% of substance is removed from the cavity by crowdion mechanism. The parameters of the heated zone have been evaluated as Po=2x10^9 Н/м2, Т=1100 К. Using light-scattering method, the crack formation in NaCl single crystals under uniaxial loading has been studied. It has been found that the cracks are predominantly positioned in {100} planes, and in minor quantity - in the {110} planes. The mechanisms of their formation are Cottrell and Stroh ones, respectively. There exists a tendency to formation of the crack compact groups.