Laser powder-bed-fusion of Si₃N₄ reinforced AlSi10Mg composites: Processing, mechanical properties and strengthening mechanisms

Laser powder-bed-fusion (L-PBF) was utilized to fabricate Si₃N₄ reinforced AlSi10Mg composites in this study. The Response Surface Methodology (RSM) was employed to optimize L-PBF processing parameters. The effects of the addition of Si₃N₄ on the mechanical properties of the L-PBFed Si₃N₄/AlSi10Mg composites were studied. The microstructures and phase of as-built Si₃N₄/AlSi10Mg composites were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffractometer (XRD). The results showed that 10 vol% Si₃N₄/AlSi10Mg composites exhibited excellent tensile strength, yield strength, elastic modulus, and microhardness, which reached 485 ± 12 MPa, 362 ± 18 MPa, 103 ± 11 GPa, and 153±3HV, respectively, when the optimal L-PBF process parameters were applied (laser power of 193 W, scan speed of 559 mm/s, hatching space of 0.048 mm). The enhancement effect stemmed from the dislocation strengthening and load transfer mechanism brought about by Si₃N₄ particles. In L-PBF: the heat conduction of the molten pool was hindered by Si₃N₄ particles, leading to a reduction of the coarse molten pool. Simultaneously, whilst the mutual diffusion of Al and Si elements occurred, no new brittle phases formed, which improved the bonding strength between the Al matrix and the Si₃N₄ particles.