Molecular dynamics study of dislocation formation processes and disorientation regions in a crystal under the influence of a laser pulse

Abstract

It is known that the impact of laser pulses on the metal surface is accompanied by such processes as local heating, melting and even evaporation of the metal, which leads to various structural changes in the surface. In particular, an extended dislocation layer can be observed under the irradiated surface. Obviously, in connection with the widespread use of lasers as a tool for processing materials, the study of the processes accompanying its impact is an urgent task, which, however, cannot always be solved exclusively experimentally and in this case, additional research methods are required. In the presented work, the molecular dynamics method is used to study the structural changes occurring in an iron single crystal subjected to relative deformation of varying magnitudes under the simulated impact of a laser pulse. When constructing the model, it is assumed that such an impact is accompanied only by heating the irradiated material to sufficiently high temperatures. During the simulation, an interphase boundary arose in the computational cell, which is a source of mechanical stresses. Its peculiarity is the presence of surface curvature, leading to uneven distribution of stresses. It is shown that as a result of subsequent structural relaxation, dislocations are formed in the crystal, which are a response to external action, and as the deformation value increases, areas of misorientation are formed. In this case, large deformations are not required for misorientation, but the presence of a liquid phase, as well as excess free volume, is necessary. It is suggested that the occurrence of dislocations and areas of misorientation is also facilitated by tangential stresses created by the interphase boundary.