Microstructure evolution during in-situ heating of AlSi10Mg alloy powders and additive manufactured parts

Micro- and nanostructure investigations of AlSi10Mg alloy powders and additive manufactured samples were performed to highlight common effects related to very fast local cooling rates during production. We refer to the homogenously dispersed Si(Mg) nanoparticles and the presence of interconnected amorphous phases in the corallike eutectic Si network and their evolution upon in situ heating in scanning transmission electron microscope. The in-situ heating experiments showed as first phenomenon at lower temperatures the crystallization of the eventually present amorphous silicon, while at temperatures above 240 degrees C coarsening into spherical crystalline particles and network breakage prevail. In addition, the Si nanoparticles evolved, mainly changing their shape and coherence with the matrix. These findings correlate with results from macroscopic investigations (DSC, insitu XRD), where they further contribute to explain the retrieved exothermic signals by linking them to the respective crystallization of the amorphous Si network, the coarsening of the finely dispersed Si nanocrystals and network breakage.