Tailoring the microstructure and mechanical properties of LPBF-fabricated AlSi10Mg alloy via combining friction stir processing and direct aging

This study examines the combined effects of friction stir processing (FSP) and subsequent direct aging (DA) on the microstructure and mechanical performance of laser-powder bed fusion fabricated AlSi10Mg alloy. FSP resulted in pronounced grain refinement, with the average grain size in the stir zone decreasing to ∼2.6 μm compared to 7.6 μm in the base metal. The severe plastic deformation fragmented the continuous Si eutectic networks into fine particles, which delayed void nucleation and enhanced ductility. After DA, precipitation occurred uniformly across all microstructural zones: both needle and particle-like precipitates. Electron backscatter diffraction confirmed the stability of the grain structure, with minimal changes in grain size or texture after DA. Mechanical testing revealed a substantial improvement in ductility after FSP (fracture strain increased 200 % ), although ultimate tensile strength (UTS) decreased (387 MPa to 247 MPa). The DA treatment restored strength, yielding a UTS of 340 MPa and fracture strain of 0.14, thus achieving a favorable balance between strength and ductility. Hardness measurements further confirmed this trend, with the stir zone increasing from ∼65 HV to 87 HV and the base metal from 105 HV to 120 HV after DA. The evolution of mechanical properties is attributed to the combined action of grain boundary strengthening, dislocation recovery, precipitation hardening, and the load-bearing role of Si phases. These results demonstrate that sequential FSP and DA processing provides an effective strategy for tailoring LPBF AlSi10Mg for structural applications.