Mechanisms of formation and accumulation of misorientations in deformable metals and alloys

Abstract

The formation of misoriented substructures in plastically deformable metal materials has been theoretically studied. Expressions are obtained for the intensity of accumulation of low-angle and high-angle misorientation boundaries. Within the framework of a mathematical model of shear plastic deformation and hardening, numerical calculations of the dependences of the average characteristics of a defective medium on the degree of deformation under conditions of uniaxial compression with a constant strain rate at room temperature are performed. It is shown that the intensity of generation of low-angle tilt walls depends significantly on the scenario of changes in the density of jogs on the screw segments of dislocation loops emitted by dislocation sources. The main mechanism for the formation of low-angle walls is the rearrangement of clusters of edge segments of dislocation loops into tilt dislocation walls under the influence of flows of interstitial atoms generated by moving screw segments. It is assumed that low-angle walls merge into one until the total misorientation angle of the merged walls reaches a critical value of about 10°, after which the distance between dislocations in the wall decreases to the corresponding critical value and further penetration of individual dislocations into the wall becomes impossible. The expression for the intensity of the formation of high-angle boundaries was obtained as a consequence of the continuation of the work of dislocation sources and the formation of clusters of low-angle walls, the total energy of which is higher than the energy of an equilibrium high-angle boundary at the same misorientation.