The secret of ABS sheets not deforming

The secret of ABS sheets not deforming

   The microstructure of deformed semi-finished products is composed of two processes, namely the gradual change of the original microstructure and the gradual establishment of new microstructure components caused by deformation. The first process is to change the size of the grains according to the deformation diagram of a certain cross-section area, and the second process is to form new grain boundaries. It is appropriate to define a region that is surrounded by a high-angle boundary (i.e., a boundary with an orientation difference greater than 10^-15) and no longer contains such a boundary as a grain. In cast metals, dendrites fit this definition.

   Extrusion and rolling experiments of single crystals prove that many new grain boundaries are generated during deformation, resulting in the transformation of single crystals into polycrystals. The more intense the process of forming new grain boundaries, the smaller the influence of the remaining factors of the original structure. New grain boundaries are formed when the original shape of the grains is difficult to change into the final shape and the blank has an obvious texture that is completely different from that of the semi-finished product. For example, when the casting grains with complex shapes are deformed and the extrusion billet becomes longitudinally thick, the violent formation of new grain boundaries can be found. In the latter case, both factors come into play because the extruded texture is very different from the rough texture.

   If the second deformation is consistent with the direction in which the grains were elongated during the first deformation (secondary extrusion, unidirectional rolling), new grain boundaries will hardly be generated. If the size of the original grains, the deformation diagram and the degree of deformation are all known, the size of the new grains can be easily calculated. Similarly, when the billet is equiaxed and there is no obvious texture (recrystallized billet), new grain boundaries are rarely formed.