A comparative study on the microstructure and strengthening behaviors of Al matrix composites containing micro- and nano-sized B4C particles

Abstract

Two types of Al matrix composites (AMCs) containing micro-sized B4C particles (m-B4C/Al) and nano-sized particles (n-B4C/Al) were prepared by hybrid accumulative roll-bonding. The influences of m-B4C and n-B4C particles on the microstructure and mechanical properties of the AMCs were investigated systematically. Microstructure observations showed that B4C particles were uniformly distributed in the matrix with well-bonded interfaces in both the two types of composites. The n-B4C/Al composites presented finer grain size compared to the m-B4C/Al, indicating that n-B4C particles are more effective in enhancing the grain refinement and suppressing the grain growth than m-B4C particles. While the n-B4C/Al composites exhibited higher microhardness and strength, the m-B4C/Al composites showed higher elongation. Moreover, the strain hardening rate of the n-B4C/Al composites was higher at the initial stage of plastic deformation, but lower than that of the m-B4C/Al composites at larger strain. Furthermore, nanoindentation tests showed an obvious increment of nanohardness with the increase of deformation in the m-B4C/Al composites. The different strengthening behaviors of m-B4C and n-B4C particles can be attributed to the particle-dislocation interactions at different stages of plastic deformation. This work demonstrated the significant differences between the deformation and strengthening behaviors of AMCs reinforced by micro- and nano-sized B4C particles, providing novel insights for the design of AMCs with high strength and toughness by taking advantages of the hybrid-sized reinforcement particles.