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High‐energy X‐rays offer the large penetration depths that are often required for determination of bulk properties in engineering materials research. Photon energies of 150 keV and more are available at synchrotron sources, depending on storage ring and insertion device. In addition, synchrotron sources can offer very high intensities on the sample even at these energies. They can be used not only to obtain high spatial resolution using very small beams, but also high time resolution in combination with a fast detector. This opens up possibilities for a wide range of in situ experiments. Typical examples that are already widely used are heating or tensile testing in the beam. However, there are also more challenging in situ experiments in the field of engineering materials research like e.g. dilatometry, differential scanning calorimetry, or cutting. Nevertheless, there are a number of applications where neutron techniques are still favorable and both probes, photons and neutrons, should be regarded as complementary. A number of in situ experiments were realized at the GKSS synchrotron and neutron beamlines and selected examples are presented in the following.

Creep damage by void nucleation and growth limits the lifetime of components subjected to loading at high temperatures. We report a combined tomography and diffraction experiment using high-energy synchrotron radiation that permitted us to follow in situ void growth and microstructure development in bulk samples. The results reveal that void growth versus time follows an exponential growth law. The formation of large void volumes coincides with texture evolution and dislocation density, reaching a steady state. Creep damage during a large proportion of sample creep life is homogeneous before damage localization occurs, which leads to rapid failure. The in situ determination of void evolution in bulk samples should allow for the assessment of creep damage in metallic materials and subsequently for lifetime predictions about samples and components that are subject to high-temperature loading.