Role of hierarchical microstructure of additively manufactured AlSi10Mg on dynamic loading behavior

Microstructure of an additively manufactured AlSi10Mg through direct metal laser sintering (DMLS) process is studied using multi-scale characterization techniques including scanning electron microscopy, electron back-scatter diffraction, and transmission electron microscopy. The microstructure of DMLS-AlSi10Mg consists of hierarchical characteristics, spanning three order of magnitude, where nanometer sized to sub-millimeter scaled features exist in the structure. These characteristics included grain and cell structures, nanoscale Si precipitates and pre-existing dislocation networks. Dynamic mechanical behavior of the material is studied using a Split Hopkinson Pressure Bar apparatus over a range of strain rates varying between 800 s(-1) and 3200 s(-1). Investigation of the deformed microstructures reveals the role of hierarchical microstructure on the dynamic behavior of the material. The high strain-rate deformation is accommodated by dynamic recovery (DRV) process, where low angle grain boundaries evolve due to the generation of dislocations, evolution of dislocation networks, and annihilation of dislocations. Both cell walls and Si precipitates contribute to impeding the dislocation motion and development of dislocation networks. At high strain rates, dislocation networks evolve in the nanoscale DRVed subgrains.