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SHEAR BEHAVIOR AND RELATED MECHANISMS IN MATERIALS PLASTICITY

# Texture Formation and Swift Effect in High Strain Torsion of NiAl

[+] Author and Article Information
Burghardt Klöden1

Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden, Germany

Carl-Georg Oertel

Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden, Germany

Werner Skrotzki2

Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden, Germanywerner.skrotzki@physik.tu-dresden.de

Erik Rybacki

Geoforschungszentrum Potsdam, D-14473 Potsdam, Germany

1

Present address: Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung, Winterbergstrasse 28, D-01277 Dresden, Germany.

2

Corresponding author.

J. Eng. Mater. Technol 131(1), 011102 (Dec 18, 2008) (10 pages) doi:10.1115/1.3030896 History: Received January 19, 2008; Revised August 07, 2008; Published December 18, 2008

## Abstract

Texture formation and Swift effect were investigated in torsion deformed NiAl. High-strain torsion of solid bars was done with a Paterson rock deformation machine at temperatures between 700 K and 1300 K under a confining pressure of 400 MPa. The maximum shear strains and shear strain rates applied were $19×10−4 s−1$ and $2.2×10−4 s−1$, respectively. Textures were measured by diffraction of neutrons, electrons, and synchrotron radiation. The textures consist of an oblique cube and Goss component, the intensity of which depends on the initial texture and deformation temperature. The axial lengthening and shortening observed are related to the Goss and the oblique cube components, respectively. There is qualitative agreement between experiment and simulation at low temperature and low shear strains. With increasing temperature, continuous and discontinuous dynamic recrystallization take place, strongly influencing the development of texture and Swift effect.

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## Figures

Figure 9

φ2=0 deg ODF sections of texture simulations for (a) ideal, (b) 10 deg, (c) 30 deg, and (d) 45 deg about the torsion axis rotated cube single orientation at different shear strains. For visualization purpose the single orientation is smoothed by 20 deg.

Figure 10

(a) Slip system activity (numbers indicate the slip systems given in Table 1, all other slip systems are inactive, and the macroscopic imposed shear rate is 1 s−1); (b) number of active slip systems, rate of plastic flow, and Taylor factor as a function of rotation of the cube orientation around TD during simple shear.

Figure 11

Length change of the samples during torsion as a function of shear strain for ⟨100⟩ (a), ⟨110⟩ (b), and ⟨111⟩ (c) oriented samples

Figure 12

Simulation of the length change for n=6 and different CRSS values: (a) ⟨100⟩, (b) ⟨110⟩, and (c) ⟨111⟩ fibers. Positive and negative values refer to lengthening and shortening, respectively.

Figure 1

Pole figures showing the initial textures of the different samples used with torsion axis in the center. Maximum intensities are given in mrd.

Figure 2

Typical shear textures of ⟨111⟩ NiAl represented as φ2=0 deg ODF sections: (a) 700 K and (b) 1000 K

Figure 3

Intensity of the cube and Goss component as a function of shear strain for ⟨100⟩ (a), ⟨110⟩ (b), and ⟨111⟩ (c) oriented samples. Open symbols correspond to the respective higher shear strain rate.

Figure 4

Temperature dependence of the cube (a) and Goss (b) component intensity at a constant shear strain of 8

Figure 5

Deviation of the cube and Goss component from the ideal position as a function of shear strain for ⟨100⟩ (a), ⟨110⟩ (b), and ⟨111⟩ (c) oriented samples. Open symbols correspond to the respective higher shear strain rate.

Figure 6

Temperature dependence of the deviation of the cube (a) and Goss (b) component from the ideal position at a constant shear strain of 8

Figure 7

(100) pole figures measured by EBSD at different positions along the torsion axis (b). The ideal cube and Goss component is shown in (a). (SD=shear direction; TD=transverse direction).

Figure 8

φ2=0 deg ODF sections of texture simulations at different shear strains: (a) initial theoretical ⟨100⟩ fiber (FWHM 9 deg, intensity 5 mrd), (b) initial experimental ⟨110⟩ fiber, and (c) initial experimental ⟨111⟩ fiber

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