Torsion Texture Measurements With High-Energy Synchrotron Radiation on NiAl

W Skrotzki,C.-G Oertel,E Rybacki,B Klöden,R Tamm,U Garbe

doi:10.1080/07303300310001628733

Abstract

Diffraction with high-energy synchrotron radiation is a new experimental method to determine textures of materials, which due to the special properties of this radiation, in the future may have advantages in terms of accuracy of local texture measurements in comparison to established methods like Electron back scatter diffraction (EBSD). In the present study NiAl polycrystals with two different initial textures have been deformed in torsion at 727°C and 1000°C and their texture development has been measured with highenergy synchrotron radiation. Torsion enables the study of texture formation with strain as well as the exploration of large strains without changing the shape of the samples. The pole figures indicate the preferred alignment of ‹100› with the shear direction and {110} with the shear plane. High pressure torsion may also open new possibilities in terms of grain refinement and texture formation and thus ductilization of NiAl.

Highlights

To measure textures in torsion deformed samples, methods with high spatial resolution have to be applied
Emphasis in this article will be put on general problems of torsion texture measurements with synchrotron radiation and problems dealing with data analysis
The fraction of LAGB goes over a maximum, i.e. there is a change in the misorientation distribution towards HAGB (Fig. 7b)

Summary

INTRODUCTION

To measure textures in torsion deformed samples, methods with high spatial resolution have to be applied. Attempts to increase the ductility of NiAl by alloying have not been successful (Noebe et al, 1996) Another way to approach this problem is to change the grain structure and texture on purpose. As the yield stress increases much slower with decreasing grain size than the fracture stress, grain refinement should help to reach the ductile field (Fig. 1) (Cottrell, 1958) This field can be extended by changing the texture in such a way that the Taylor factor is reduced. In order to optimize the desired mechanical properties by thermomechanical treatment, it is of particular interest to understand the mechanisms of grain structure and texture formation during deformation and annealing To approach this aim, torsion has been used. Emphasis in this article will be put on general problems of torsion texture measurements with synchrotron radiation and problems dealing with data analysis

EXPERIMENTAL

Problems Related to the Variation of the Shear Direction

RESULTS

DISCUSSION