11. Texture properties

200°C showed positive sloped curves because of their low L/W ratio. These findings

A crystal is characterized by the periodic arrangement of its elements (atoms, ions) in space. In the field of material science and engineering, the distribution of the crystallographic orientations of a polycrystalline sample is called as texture. If these orientations were fully random in a sample, it had no texture. If the crystallographic orientations have some preferred orientation but were not random, then the sample has different textures, namely, weak, moderate and strong. The crystal having the preferred orientation and its degree was dependent on the percentage [6]. Texture can have a great influence on the material properties and is seen in almost all engineered materials. If all crystallites had the same orientation, the anisotropy of the polycrystal exactly equals that of the single crystal [7]. In an isotropic texture, all orientations occur with the same probability; the behaviour of the polycrystalline material was isotropic even though every single element (crys-

Texture can be determined by various methods, namely, quantitative analysis and qualitative analysis. In quantitative techniques, the most widely used is X-ray diffraction using texture goniometry. Often texture has been represented using a pole figure, in a stereographic projection, a specified crystallographic axis (or pole) from each of which a representative number of crystallites which was plotted, along with the directions relevant to the material's processing history. These defined

The commonly found textures in processed materials are cube (0 0 1)<100>, brass (1 1 0)<112>, copper (1 1 2)<1 1 –1> and S(1 2 3)<6 3 –4> [9]. These were

The ODF is defined as the volume fraction of grains with a certain orientation. The orientation is normally identified using three Euler angles. The orientation distribution function cannot be measured directly by any technique. But it can be state by a sum of functions or expand it in a series of harmonic function [9]. Others, known as discrete methods, divide the ODF space in cells and focus on determining

The making of metal sheet often involves compression in one direction and, in efficient rolling operations, tension in another, which can orient crystallites in both

annealing usually have a different texture [7]. The control of texture was extremely important during the making of a silicon steel sheet for transformer cores (to reduce

axes, by a process known as the grain flow. New crystallites that arise with

were in good agreement with those of Narayanasamy et al. [1, 26].

tallite) showed an anisotropic behaviour (Engler et al., 2001).

10.1 Crystallographic texture analysis

10.2 Common textures

directions are called as a sample reference frames.

given in miller indices for simplification purposes.

10.3 Orientation distribution function

the value of the ODF in each cell.

10.4 Origin

48

10. Crystallographic texture

Aluminium Alloys and Composites

Texture significantly affects the formability which is usually evaluated in terms of forming limit diagrams [1]. Although much research has been carried out, their correlations have not yet been completely clarified. Aluminium alloys exhibit typical pure metal texture (Cu-type) on rolling comprising of Cu {1 1 2}<111>, brass {1 1 0}<112> and S {1 2 3}<634> orientations, and Cube {1 0 0}<001 > and Goss {1 1 0}<001> components were common during annealing [7, 10]. In this aspect an attempt has been made to correlate the tensile properties, formability properties and void coalescence parameters, with texture of sheet metal at different annealing temperatures. The effect of the cube texture on the initiation of localized necking has been studied using numerical methods by Wu et al. [12]. They have inferred that, when a sheet undergoes biaxial tension, ideal cube texture significantly delays the initiation of localized necking [11]. Aluminium alloys exhibit typical pure metal texture (Cu {1 1 2} <111>-type) on rolling comprising of Cu {1 1 2}<111>{1 1 2}<111>, brass {1 1 0}<112> and S {1 2 3}<634> orientations, and Cube {1 0 0}<001> and Goss {1 1 0}<001> components are common during annealing [10] as seen in Figure 1. An Al 8011 aluminium alloy sheet cold-rolled by 95% had a typical fibre texture, which runs from the copper orientation {1 1 2}<1 1 1> over the S-orientation {1 2 3}<634> to the brass orientation {1 1 0}<112> in the Euler space. The results were discussed, based on the interaction between precipitation and recrystallization [13, 14]. The cube component recovered quite easily during deformation after large strains as well as during the first step of the annealing treatment, as per the findings of Gerber et al. [15].

Matthies et al. [16] have consolidated all methods of the analysis of texture by pole figure and orientation distribution function (ODF) in Euler space. Knorr et al. [17] and Kocks et al. [18] studied the material property such as strength and deformation behaviour, through texture and failure analysis. Bennett et al. [6] examined the cube (1 0 0)<001> grains before and after stretching and found that there was a translocation. In this aspect this work investigates the mode of evolution of texture components, in commercially available aluminium alloy sheets of three different thicknesses at three different annealing temperatures using numerical modelling practice. The works related to the crystal plastic models are given below. From the results of Al 8011, Al 1145 and Al 1350 alloy, pole figures ODF and alphabeta fibre, the following discussions were made (Figure 17).
