Materials Science and Engineering, A 186 ( 1994) 35-44 35 Crystallographic texture gradients in the aluminum 8090 matrix alloy and 8090 particulate composites M. A. Przystupa Department of Materials Science and Engineering, University of California, Los Angeles, CA 90024 (USA) A. K. Vasud6van Office of Naval Research, Code-1222, 800 N. Quincy St., Arlington, VA 22217 (USA) A. D. Rollett Los Alamos National Laboratory, Mail Stop G770, Los Alamos, NM 87545 (USA) (Received March 16.1993; in revised form November 9, 1993) Abstract AI-Li alloys develop sharp textures with a strong brass component after fabrication. In the case of thick sheet and plate extrusions through thickness texture gradients are also commonly observed. These textures are different from those that develop in conventional aluminum alloys and their origin has not yet been completely understood. In the present work the sources of texture gradients in the 8090 alloy and 8090 based particulate composites, both formed as thick plate extrusions, have been studied. Results showed that strain gradients, and redundant shears in particular, are responsible for the development of textures in the 8090 alloys. In the SiC reinforced particulate composites, the presence of reinforce- ment resulted in the development of significantlyweaker deformation textures without dominant brass component within the plate and a mixture of recrystailization and surface shear type textures at the surface. The development of textures in the composites has been attributed to the absence of redundant shears in the bulk and to a surface deformation gradient introduced by the presence of SiC particles. 1. Introduction In most f.c.c, metals and alloys deformation textures consist of a family of orientations, called the fl-fiber, extending from the {101}(121) (brass) to the {112}(1i 1) (Cu) component [1]. For pure aluminum and its conventional alloys the deformation textures are of the copper type, which means that most of the grains have orientations closer to the Cu end of the fl- fiber. The exceptions are A1-Li alloys. Instead of the copper type texture, characteristic of high stacking fault energy (SFE) f.c.c, materials like conventional AI alloys, these alloys often exhibit strong brass-like texture, characteristic of low SFE materials [2, 3]. In this case, however, the transition to brass texture is probably not the result of lower SFE (especially as the modulus goes up, therefore lowering the SFE/ktb). Instead, the effect of Li addition is to make the slip within the grains much more planar. Increased planar- ity of slip leads to brass-like texture for reasons that are still the subject of debate. The peak texture intensities in AI-Li alloys are also exceptionally high, which results in a strong directionality of mechanical prop- erties. For instance, the yield strength anisotropy in the A1-Li 2090 alloy can reach up to 20% at peak strength [2, 3]. The deformation textures in the AI-Li extrusions and/or rolling products also exhibit both through thick- ness gradients and evidence of non-uniform surface shears [2, 4-6]. These textures tend to have a strong brass component at the plate or extrusion center, and a weak fl-fiber at the surface. Additional texture com- ponents from surface shear are, when present, of the {001}(110) type [4, 6]. The origin of such deforma- tion textures has so far been studied by only a few investigators [4, 5, 7, 8] and questions regarding the mechanisms controlling their development remain unresolved. One of the possible methods of altering deformation textures in AI-Li alloys, and polycrystals in general, is to change the slip patterns in all the grains by changing either (a) macroscopic or (b) microscopic strains during formation. The first of these methods requires changes in tooling, which is expensive and difficult to execute. The second involves changes in the microstructure, which can be made by the addition either of solute that 0921-5093/94/$7.00 © 1994 - Elsevier Sequoia. All rights reserved SSD1 0921-5093(93)09480-7