Effect of strontium salt modification on the microstructure and creep properties of SLM-formed SiC/AlSi10Mg composites

In this study, two different Al matrix composites reinforced with 3 vol% SiC particles were fabricated via selective laser melting (SLM) by using both pure AlSi10Mg powder and Sr-modified AlSi10Mg powder as the matrix materials. Their microstructure and high-temperature creep property were investigated in parallel with each other. Results demonstrated that Sr modification refines the microstructure significantly in terms of the average width of eutectic silicon networks (80.9 → 72.4 nm), the average size of Al cells (392.3 → 320.0 nm) and the average grain size (12.12 → 10.34 μm). Furthermore, Sr modification decreases the strength of <001> texture along build direction from 5.57 to 3.48. Creep testing revealed that Sr modification enhances the creep life from 4.43 h to 19.1 h, corresponding to 331% improvement. The underlaying mechanism was elucidated via microstructural characterization and simulation analysis. Results showed that the refined eutectic silicon networks and uniformly distributed SiC particles effectively pin dislocations and inhibit micro-voids formation. Meanwhile, the concentration gradient diffusion of dissolved Si in the Al matrix delays coarsening of silicon particles, which in turn enhances creep resistance stability. This work may provide some guidance for the development of Al matrix composites for high-temperature applications.