Microstructure and Mechanical Properties of B4C/6061Al Nanocomposites Fabricated by Advanced Powder Metallurgy

In this study, B4C/6061Al nanocomposites reinforced with various volume fractions of nano-sized B4C particles (B4C/6061Al NCs) are successfully fabricated by a powder metallurgy route consisting of spark plasma sintering (SPS) and hot extrusion and rolling (HER). The microstructure evolution, phase composition, and mechanical properties of B4C/6061Al NCs are experimentally investigate. The results show that nearly fully dense (maximum approximate to 99.21%) as-SPSed NCs can be fabricated, and this can be attributed to joule heating at the particle contacts and tip spark plasma at the gaps. Nanosized B4C particles mainly distributed in the 6061Al particles boundaries and formed inhomogeneous network materials in as-SPSed NCs, while B4C particles distributed relatively homogeneously in the 6061Al matrix after HER. No new phases are found in the B4C/6061Al NCs over three deformation stages. The pin effect of the nanosized B4C can suppress dynamic recovery and improve the driving force for dynamic recrystallization. The mechanical properties are further improved after HER, and the maximum ultimate tensile strength and yield strength for as-rolled NCs are 305 and 168MPa. The strengthening mechanisms mainly included load transfer strengthening, dislocation strengthening, Orowan strengthening, and fine-grain strengthening.