Hypervelocity impact response and microstructure evolution of microporous PBF-LB AlSi10Mg

To clarify the dynamic response of additively manufactured aluminum alloys containing microporosity under hypervelocity impact, this study integrates hypervelocity impact recovery experiments, multiscale microstructural characterization, and nonequilibrium molecular dynamics (NEMD) simulations to systematically investigate the pore-collapse behavior and microstructural evolution of laser beam powder bed-fused (PBF-LB) AlSi10Mg. The experimental results show that most pores are nearly completely closed under the lower-velocity impact condition, whereas the coupled effects of multiple mechanisms, including shock-wave reflection and superposition during unloading, induce an increased population of post-impact micropores under the higher-velocity condition, accompanied by pronounced localized melting in the vicinity of the pores. The microstructural characterization further indicates a corresponding shift in the dominant deformation response, from dislocation multiplication and grain refinement at the lower velocity to dynamic recovery, thermal softening, and localized melting–resolidification at the higher velocity. Based on the characterization results, a pore-containing Al–Si layered atomistic model was constructed to represent the local microstructural features of the material. The simulations reveal a pronounced velocity-dependent transition in pore-collapse mechanisms: shear-stress-driven plastic collapse predominates at lower impact velocities, whereas normal-stress-driven melt micro-jetting becomes dominant at higher velocities. To quantitatively characterize the governing role of pore geometry, size, spatial location, and shape factors were introduced and linked to the thermodynamic response through normalized response functions. These findings establish a quantitative, mechanism-based framework for understanding the defect-controlled hypervelocity response of additively manufactured aluminum alloys.