Fabrication, microstructure characterization and mechanical properties of B4C microparticles and SiC nanowires hybrid reinforced aluminum matrix composites

Due to the high modulus, high strength , low density, excellent wear resistance and good neutron absorption, the boron carbide (B 4 C) particle reinforced aluminum (Al) matrix composites have been widely applied in the aerospace, weaponry, transportation and neutron shielding fields. In response to the increasing requirement of better strength -ductility matching of B 4 C/Al composites, introducing a nano-scale reinforcement into the B 4 C/Al composites becomes an attractive research focus. In this work, the SiC nanowires were ball-milled with Al powders, and then the SiC/Al composite powders were mixed with B 4 C microparticles . Thus, the 15vol. % B 4 C/SiC/Al composites with different volume fractions of SiC nanowires were fabricated by hot-pressing sintering and hot extrusion. B 4 C microparticles and SiC nanowires are uniformly dispersed in the B 4 C/SiC/Al composites, while the introduced SiC nanowires effectively decrease the Al matrix grain sizes . B 4 C/SiC/Al composites produce the better strength-ductility matching than that of B 4 C/Al composites, while the 15vol. % B 4 C/SiC/Al composite with 1vol. % SiC nanowires achieved the best strength-ductility matching. It generates the 281.7 ± 2.7 MPa in yield strength, 351.2 ± 0.1 MPa in ultimate tensile strength and 5.9 ± 0.7% in failure elongation, which are increased by 18.2%, 15.1% and 13.5% compared to the B 4 C/Al composites. Uniformly dispersed B 4 C microparticles and SiC nanowires largely block the dislocation motions and improve the dislocation storage capacity, which results in a more significant hetero-deformation induced (HDI) hardening effect in the B 4 C/SiC/Al composites. Moreover, the B 4 C/Al interfacial transition regions with the added SiC nanowires becomes stronger, which can enhance the load transfer efficiency of the B 4 C/Al interfaces as a result of the existing dislocation hardening zones. In conclusion, it is a good strategy to combine the synergistic strengthening effect of micro-scale and nano-scale reinforcements in the metal matrix composites .