The following instruments are available:
for the study of residual stress, textures, phases and nano-structuresE-mail contact
Contact: Dr. Norbert Schell
for studies of the grain structure of materialsE-mail contact
Contact: Dr. Caroline Curfs
for spatially resolved studies of, e.g., of near-surface residual stresses and phasesE-mail contact
Contact: Dr. Thomas Wroblewski
for the study of residual stress, textures and phases at the surfaceE-mail contact
Contact: Dr. Dieter Lott
for the study of nano-structures like, e.g., precipitatesE-mail contact
Contact: Dr. Dieter Lott
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.
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.
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.
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.
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.
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.