Inhomogeneous Structures in Extruded Aluminium Single Crystals

Abstract

It is wellknown that the formation of deformation bands exerts an important influence on the development of the ⟨100⟩ fiber texture in drawn or extruded fcc metals. It is considered that slip on different systems caused by a constrained plastic flow under an axially-symmetric deformation results in band formation. However, lattice rotation in the bands during deformation, especially the formation process of the ⟨100⟩ component, has not been analysed in detail. In this work, the formation of deformation bands along flow directions in the plastic zone was studied with extruded rods of aluminium single crystals. The following results were obtained:
(1) The difference in band appearance, which depends on the initial orientation of the crystal, results from the difference in the distribution of “unit patterns”.
(2) A unit pattern is composed of two regions. Region A in which the ⟨111⟩ component is dominant located at the center of the unit pattern. In region B on four sides of region A, each ⟨100⟩ component exists on toothed boundaries between two ⟨111⟩ components. In the other regions the ⟨111⟩ component is dominant.
(3) The area where flow directions in the plastic zone are in the range of ⟨001⟩∼⟨011⟩∼⟨112⟩ on the stereographic triangle becomes the origin of unit pattern. Flow directions ranging from ⟨013⟩ to ⟨112⟩ determine the boundary between A and B.