Abstract With the advantage of micro-size and nano-size B4C particles, micro-/nano-bimodal size B4C particles have been widely used to fabricate excellent composites with high strength and ductility. In this study,… Click to show full abstract
Abstract With the advantage of micro-size and nano-size B4C particles, micro-/nano-bimodal size B4C particles have been widely used to fabricate excellent composites with high strength and ductility. In this study, micro-/nano-bimodal size B4C particles reinforced aluminum matrix composites with three different volume fractions (3%, 5% and 7%) were fabricated by spark plasma sintering (SPS) followed by hot extrusion and rolling (HER). The microstructure evolution and mechanical properties of as-SPSed, as-extruded and as-rolled composites were investigated. Results show that the microscopic electrical discharge between the particles in SPS promotes the densification of composites. The maximum relative density of as-SPSed composites increases from 99.21% to 99.65% after HER. Nano-size B4C particles distribute mainly at the gap of 6061Al particles in as-SPSed composites, while the microstructure presents more homogeneous after HER. Pin effect of nano-size B4C particles stimulates dynamic recrystallization (DRX) and grain refining. Texture orientation of the 6061Al grain exists in the as-extruded and as-rolled B4C/6061Al NCs. No new phases are detected in composites in all deformation stages. The tensile strength of as-SPSed composites increases when compared with 6061Al matrix, and the tensile strength of as-rolled composites after hot extrusion is enhanced to 305 MPa. Fracture mechanisms of as-extruded and as-rolled composites mainly include 6061Al matrix tear, particle/matrix interfacial tear and micro-size B4C particle fracture.
               
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