Rotation of crystal lattice induced by the development of dislocation slip in flat two-dimensional polycrystalline samples of aluminum with a “pancake” grain structure

Abstract

In this paper presented the results of the rotation of the crystal lattice of grains in flat samples of two-dimensional polycrystals of aluminum with a “pancake” grain structure ”with an average grain size  mm and initial dimensions of the working section 100 mm (length), 20 mm (width), 0.15 mm ( thickness). Rotation of the grain crystal lattice occurs as a result of dislocation sliding during deformation of the samples by tension under active loading at a constant strain rate  at room temperature. The features of such samples are following: there is only one layer of grains in the cross section and their sizes in the directions of the length and width of the sample significantly exceed the thickness of the sample; there is no constraint of the grain structure along the thickness of the sample. As a result, there is no constraint of plastic deformation in this direction. Experiment shows that slip deformation occurs predominantly in one slip system.

According to the well-known theoretical concepts of rotational plasticity, a model is proposed for the rotations of the crystal lattice of grains, which are caused by the action of one slip system. Calculations show that the trajectory of rotation of the tension axis on the plane of the stereographic projection is a circular arc, which is defined by the initial position of the tension axis. The equation for such a circles is obtained. Two cases of mutual arrangement of the tension axis, the normal to the sliding plane and the sliding direction are possible. If the initial crystallographic orientation of the grain is such that the tension axis lies in the plane of the sliding direction and normal to the sliding plane, then tensile axis during the lattice rotation will be moving towards the sliding direction until it coincides with it. In this case, the tensile axis rotation traces cross point [101] as for a single crystal sample. In other case, when the directions of the tensile axis, sliding and normal to the sliding plane are not coplanar, then rotation trace does not pass through the point [101], but follows circular arc as mentioned earlier.

Comparison of the experimental data of the tensile axis rotation traces (based on the results of X-ray studies) with the calculated traces proposed by model (with one active slip system) shows their good agreement.