Modeling of healing pores of cylindrical form under the action of shock waves in a crystal subjected to shear deformation

Abstract

Volumetric defects in crystals worsen operational properties of structural materials; therefore, the problem of reducing discontinuities in solid is one of the most important in modern materials science. In the present work, the results of computer simulation are presented that demonstrate possibility of collapse of pores in a crystal in state of shear deformation under the influence of shock waves. Similar waves can occur in a solid under external high-intensity exposure. For example, in the zone of propagation of displacement cascade, there are regions in which occurs a mismatch between the thermalization times of atomic vibrations and the removal of heat from them. As a result of the expansion of such a region, a shock after cascade wave arises. The simulation was carried out based on molecular dynamics method using the potential calculated by means of mmersed atom method. As a bulk defect, we considered extended pores of cylindrical shape, which can be formed after passing of high-energy ions through a crystal, or, for example, when superheated closed fluid inclusions (mother liquor) reach the surface. The study has shown that such defects are the source of heterogeneous nucleation of dislocation loops, contributing to a decrease in the shear stresses in simulated structure. Dependences of the average dislocation density on the shear angle and temperature of the designed cell were established, and the loop growth rate was estimated. Generated shock waves create additional tangential stresses that contribute to the formation of dislocation loops; therefore, in this case, dislocations are observed even with a small shear strain. If during simulation the thermal effect increases, the pore collapses.