Evolution of Crystallographic Texture in Cold Rolled Al-Zn-Mg Alloys Used in Space Applications

Abstract

The aerospace industry uses a variety of materials in different forms like sheets, forgings, extruded rods, welded components and machined components for launch vehicle and satellite applications. As lighter and stronger materials are the aims of the aerospace industry, aluminium alloys are the most widely used materials in the in the aircraft and aerospace industries. These aluminum alloys used in the aerospace industry are subjected to a variety of processing operations, either in the sheet form after rolling, forging, heat treatment and machining conditions, to realize the final product implies that these alloys exhibit a wide range of properties depending on the processing conditions. Texture formation in a material takes place during its various processing stages. The actual orientation distribution in a poly crystal is the result of the manufacturing processes applied. In this context, it is important to characterize the evolution of texture, both macro and micro texture, in AA7075 and AFNOR7020 alloys, which are two of the important high strength aluminum alloys used in the Aerospace industry. This paper deals with the results of the crystallographic texture measurements carried out on the cold rolled and artificially aged AA7075 and AFNOR7020 aluminium alloys. Results obtained from the pole figure analysis, Orientation Distribution Function (ODF) method and estimation of the various fibres present in the cold rolled material and the volume fraction of the texture components are discussed in detail for the alloy. Results of the micro texture measurements using the EBSD are presented, explained and analyzed in detail. A comparison of the inverse pole figures (IPFs), Image Quality (IQ) maps, Misorientation angle, Grain Orientation Spread (GOS), Kernal Average Misorientation (KAM), CSL boundaries, Grain size and Grain boundary character distribution (GBCD) for materials cold rolled to different reduction for the alloy are done and analyzed. Conclusions are drawn regarding the evolution of texture from the above analysis. Deformation texture components Cu, Bs and S increase from the starting material as the rolling percentage increases. On the other hand, recrystallization texture components of Goss and Cube are observed to be weak. AFNOR7020 Alloy developed a stronger texture compared to the AA7075 alloy. S component of texture is stronger in AA7075 alloy whereas the Bs component is stronger in AFNOR7020 alloy. This is attributed to the shear banding which was found absent in the other alloy.