Aluminum matrix composites have the characteristics of high hardness and difficult machining.In order to achieve near-net forming of aluminum matrix composites with high specific strength and high specific modulus,micron SiC particles with volume fraction of 10%reinforced AlMgScZr composites were fabricated using selective laser melting(SLM)technique.The relationship between the laser energy density and scanning rate and the forming quality of the composite was established.The microstructure and mechanical properties were characterized and tested by optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM),X-ray diffraction(XRD)and universal testing machine.The effect of micron SiC particles on the solidification structure and mechanical properties of SLMed aluminum matrix composites was investigated.The results show that the best quality composite could be obtained under the conditions of layer thickness of 30 μm,scanning spacing of 0.12 mm,laser power of 260 W,scanning rate of 1 000 mm/s,and its relative density was up to 99.81%.During the laser cladding process,there was a strong interfacial reaction between SiC particles and Al matrix.Micron-sized acicular Al4SiC4 bands were formed in situ,and the sharp corners of SiC particles are obviously passivated.Al4SiC4 bands and the residual SiC particles formed a mixed reinforced structure.The optimal tensile strength,elongation and elastic modulus of aged SiC/AlMgScZr composites were 379 MPa,12%and 84 GPa,respectively.The fracture behavior of the composites included ductile fracture of Al matrix and brittle cleavage fracture of Al4SiC4 phases.A large number of cross-distributed acicular Al4SiC4 bands were the main factors leading to premature failure and fracture of SiC/AlMgScZr composites.
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