A new approach to three-dimensional x-ray diffraction(3DXRD) using hard x-rays allows for the first time an in-situ mapping of deformation mechanisms deep in the bulk of a complex 3D printed steel sample.
The strength and deformation behaviour of egineering metals depends in a complex way on both the chemistry and microstructure of the metal. Plastic deformation works by the generation and subsequent movement of crystallographic defects such as dislocations, deformation twins, and phase transitions. Understanding the processes involved requires experimental methods that can probe changes to the microstrucure in-situ.
Hard x-ray diffraction is one of the few non-destructive methods which can be used to study the evolution of microstructure in bulk material, but typically only information about the average structure over the whole sample can be obtained. 3DXRD is a family of techniques that enable spatially resolved diffraction measurements using algorithms similar to computed tomography. Researchers at PSI have demonstrated that a new method, called texture tomography can be used to study more complex microstuctures than has so far been demonstrated. Using the hard x-rays available at the Diffraction and Imaging Beamline p21.1 at PETRA III, the microstructure inside a millimeter thick sample of 3D printed TWIP steel can be spatially mapped and followed over a tensile deformation of 20%.
The resulting maps display both reorientation of the crystal grains by a phenomenon know as slip as well as the formation of tiny new twin crystals inside the existing grains. The study published in Materials Research Letters shows that texture tomography has potential as a new way to probe the processes that determine the mechanical performance of metals and to guide the development of better materials for the future.