High-resolution microstructure investigations of additive manufactured parts

Characterization at very high resolution facilitated fundamental understanding of atomic effects and processes in materials and therefore opened a new era in materials design. The micro- and nanostructure morphology, chemical composition and functionality are crucial for development of materials for field-specific applications.
Within this paper a correlative study of ex- and in-situ heating experiments performed on additive manufactured parts is presented. Scanning and transmission electron microscopy (SEM and S/TEM) characterization methods were used for advanced microstructural analysis of the feedstock at first and of the as-built and heat treated parts. Evolution of the microstructure during the ex-situ heat-treatment was first studied in detail in order to better comprehend the mechanical properties of the printed parts.
Scanning TEM acquisition of high angular annular dark field images (HAADF) as well as hyperspectral analysis by X-ray (EDX) and electron energy loss spectrometry (EELS) were used to localize and identify the elements and their stable and metastable phases.
Additionally, we performed in-situ heating measurements at high spatial resolution in order to provide information regarding the crystallization of amorphous phases and coarsening/shrinking of grains, diffusion of alloying elements and nucleation and evolution of secondary phases at different temperatures.
By comparing scanning calorimetry measurements with the in-situ heating investigations, we could determine the relative temperature at which a specific phase crystallization and transformation takes place.