In-situ High Energy Synchrotron X-ray Diffraction of Laser Materials Processing

Important results from the project

Short thermal-cycle laser beam heat treatments induces phase transformations in steels, while the resulting microstructures deviate from the typical phase transformation at longer thermal cycles. Therefore, this project aimed to observe and explaine the dynamics of phase transformation in steels during short-thermal-cycle laser heat treatment using synchrotron X-ray. The results of this project can be used for advanced tailoring of microstructures by laser heat treatment.

Expected long term effects

The acquired diffraction data contain information about changes in the lattice structures over time during laser pulse illumination. It was observed that the diffraction peaks shifted towards higher values during the illumination. Such profound shift was observed in the area close to the specimen surface and weakened towards the depth of the specimen. This behaviour indicates stresses in the lattice during the process, which is related to the heat conductivity of the material.

Approach and implementation

Reconstruction of the lattices is carried out from each diffraction data collected over time during laser illumination. 250 frames per second were recorded, while each frame contains the information at the specific time. Those reconstructions are used to describe and explain at which temperatures they start and stop being created. Various process conditions were tested, which enables the explanation how the processing parameters and alloying elements influence the lattice dynamics.