X-Ray Diffraction with Synchrotron Radiation

Methods

Bild Instrumente Und Methoden Wpd

The following instruments are available:

• HEMS – High-Energy Materials Science Beamline (P07):

for the study of residual stress, textures, phases and nano-structures

Contact: Dr. Norbert Schell

E-mail contact

• HEMS Grain Mapper:

for studies of the grain structure of materials

Contact: Dr. Torben Fischer

E-mail contact

• High-Energy Materials Science Beamline with white beam (P61.1, starting in 2019):

for spatially resolved studies of, e.g., of near-surface residual stresses and phases

Contact: Dr. Thomas Lippmann

E-mail contact

• RÖDI – Lab-X-ray diffractometer:

for the study of residual stress, textures and phases at the surface

Contact: Dr. Dieter Lott

E-mail contact

• NanoStar – Lab-small-angle scattering instrument:

for the study of nano-structures like, e.g., precipitates

Contact: Dr. Dieter Lott

E-mail contact

In the following the most important methods are described.

Note that we are using high photon energies (50 … 150 keV) for penetration deep into material.

• Diffraction – phase analysis

For the quantitative determination of phase contents of a material.

Wpd - Gestapelte Diffraktogramme

The example is about the development of laser welding as a joining technique for TiAl alloys. The image shows a stacked diffractogram plot during an in-situ laser welding experiment. Melting (stage 2), solidification (stage 4) and phase transformations (stage 5) in a TiAl alloy could be observed with a time resolution of 100 ms.

J. Liu et al., Metall. Mater. Trans. A (2016) DOI: 10.1007/s11661-016-3726-x

• Diffraction – residual stress analysis

For the determination of residual stresses in the interior of materials and components. Conical slits are available for spatial resolution along the beam.

Wpd - Laser Shock Peening

The example is about laser shock peening (LSP) of Al alloys. LSP is a surface treatment that can improve fatigue properties. The picture shows the distribution of residual stress in a CT sample with a laser shock peening treatment (area marked with dashed lines).

N. Kashaev et al., Intern. J. Fatigue 98 (2017) 223–233.

• Diffraction – texture analysis

For the determination of the crystallographic textures of the phases present in a material.

Wpd - Lasergeschweißte Bleche

The crystallographic texture of a material can have a strong influence on the anisotropy of mechanical properties. It also affects residual the stress distribution which in turn influences fatigue properties of welds. This influence was studied in laser beam welded Ti alloy sheets. The picture shows how samples with different orientations of the rolling direction with respect to the welding direction were selected.

E. Maawad et al., Materials & Design 101 (2016) 137–145.

• Diffraction – grain mapping

3DXRD for the determination of position, orientation and internal strains of all grains within a gauge volume.

Wpd - Martensitbildung

The example is about martensite formation in an austenitic Fe-Cr-Ni alloy during cooling. The single-grain data indicated that stacking faults appear as precursors to the martensite. The picture shows a diffraction pattern with single diffraction peaks (a) and a peak profile with fit (b).

Y. Tian et al., Scripta Mater. 136 (2017) 124–127.

• Diffraction – energy-dispersive

For the determination of phase content, residual stresses and textures with position and time resolution within a fixed gauge volume. (Starting in 2019.)

• Small-angle X-ray scattering (SAXS)

For the analysis of nano structures like e.g. precipitates.

Wpd - Saxs-signal Und Tem-bild

Intermetallic TiAl alloys of the latest generation exhibit the potential to be used in modern high-performance combustion engines. Doping alloys with carbon can further improve the performance by solid solution hardening or carbide formation. The thermal stability of the carbide precipitates needs to be tested under service conditions. The picture shows a SAXS signal of carbides (left) and a TEM image of carbides inside the lamellar microstructure (right).

E. Schwaighofer et al., Acta Mater. 77 (2014) 360–369.