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 (B4C) 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 B4C/Al composites, introducing a nano-scale reinforcement into the B4C/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 B4C microparticles. Thus, the 15vol. % B4C/ SiC/Al composites with different volume fractions of SiC nanowires were fabricated by hot-pressing sintering and hot extrusion. B4C microparticles and SiC nanowires are uniformly dispersed in the B4C/SiC/Al composites, while the introduced SiC nanowires effectively decrease the Al matrix grain sizes. B4C/SiC/Al composites produce the better strength-ductility matching than that of B4C/Al composites, while the 15vol. % B4C/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 B4C/Al composites. Uniformly dispersed B4C 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 B4C/SiC/ Al composites. Moreover, the B4C/Al interfacial transition regions with the added SiC nanowires becomes stronger, which can enhance the load transfer efficiency of the B4C/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.