Texturentwicklung nanokristalliner W-Cu Komposite

Translated title of the contribution: Texture evolution in nanocrystalline W-Cu composits

Anna Rodriguez Chavez

Research output: ThesisDiploma Thesis

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Abstract

In the last decades the method of Severe Plastic Deformation has gained scientific interest due to promising results of their material properties. The size of the grains lies in a range of 50 nm to 1 µm. This leads to higher material strength. There are three main methods of severe plastic deformation: Equal Channel Angular Pressing (ECAP), Accumulative Roll Bonding (ARB) and High Pressure Torsion (HPT). This thesis reports on the studies of texture evolution of the microstructure for pure copper, pure tungsten and the composite of both. Applying the High Pressure Torsion method the required parameters like temperature, deformation speed, strain rate and deformation force are easy to vary. The metals were compared with the help of different texture analysis methods like texture calculated from Electron Backscattering Diffraction (EBSD) pictures, diffraction patterns from X-Ray analysis and diffraction images from Transmission Electron Microscopy (TEM). The comparison of the images of the texture analysed by EBSD und X-Ray for pure copper and tungsten agree with the ideal components of the shear texture although there is a loss of intensity of the X-Ray diffraction reflection. For the composite material the two different analysing methods exhibited a resemblance only for the diffraction planes {110} and {310} of tungsten. The two methods do not show correlation for the planes {200} and {211}. The texture components, tungsten and copper, of the composite analysed with EBSD develop a weak texture at low strains, which still stays weak under increasing strains. Tungsten obviously determines the fragmentation process during deformation. While copper is already in the saturation microstructure with a grain size of 5-20 nm few larger tungsten grains still break apart. To study the possible change of the texture of a grain after fragmentation, positions of equal strain were analysed with EBSD. Areas of unbroken and broken grains were separately interpreted and showed that the texture did not change.
Translated title of the contributionTexture evolution in nanocrystalline W-Cu composits
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Pippan, Reinhard, Supervisor (internal)
Award date18 Dec 2015
Publication statusPublished - 2015

Bibliographical note

embargoed until null

Keywords

  • texture
  • nanocrytalline
  • severe plastic deformation
  • high pressure torsion
  • composite

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