Microstructural evolution and mechanical performance of nano-Nb-modified AlSi10Mg alloy fabricated by laser powder bed fusion

In this study, nano-Nb-modified AlSi10Mg composites were fabricated using laser powder bed fusion (LPBF). The effects of Nb addition on the microstructure and mechanical properties of the AlSi10Mg alloy were systematically investigated. Compared with the as-built AlSi10Mg alloy, the microstructure along the building direction of the AlSi10Mg–Nb composites changed from coarse columnar grains to ultrafine equiaxed grains. Moreover, the preferential grain growth orientation was significantly weakened. Grain refinement occurs due to the presence of abundant in-situ Al3Nb precipitates dispersed within the grain, serving as heterogeneous nucleation inoculants. Simultaneously, the precipitation of NbSi2 particles along the eutectic network also contributed to refining the structure of the eutectic network. As a result, the LPBF-processed AlSi10Mg–Nb samples demonstrated a very high ultimate tensile strength (∼560 MPa) and good ductility (∼7%), comparable to those of high-strength aluminum alloys. The underlying mechanisms for this strength enhancement are discussed based on the improved mechanical properties. This study provides a novel perspective for the fabrication of high-performance AlSi10Mg alloys using LPBF.