Metal Additive Manufacturing Conference 2019

This paper presents an advanced microstructural analysis of the powder as well as of the as-built and heat treated additive manufactured parts of Al-alloy and N700 steel. Evolution of the microstructure during the heat-treatment was studied in detail in order to better understand the mechanical properties of the printed parts. For crystallographic and chemical characterization down to atomic resolution, ex- and in-situ scanning and scanning transmission electron microscopy (SEM and HR STEM) were involved. STEM acquisition of high angular annular dark field images (HAADF) and differential phase contrast images, as well as both X-ray (EDX) and electron energy loss spectrometry (EELS) spectrum images, were used to localize and identify the elements and their stable and metastable phases. In-situ STEM observations provided information regarding the crystallization of amorphous phases and coarsening/shrinking of grains, diffusion of alloying elements and nucleation of secondary phases at different temperatures.