Microstructure and enhanced mechanical properties of hybrid-sized B4C particle-reinforced 6061Al matrix composites

In the present work, the microstructure and elevated-temperature tensile properties of 6061Al alloy and 6061 Al matrix composites reinforced with bimodal-sized (micron + nano) B4C particles or monomodal micro-sized B4C particles are investigated. The results demonstrate that nanoscale B4C (n-B4C) particles are present both at the grain boundaries and within the grains in the composite. Due to the presence of n-B4C particles, there is a decrease in matrix grain size and recrystallization region percentage, and an increase in proportion of low angle grain boundaries. The combined mechanical property and theoretical analyses reveal that n-B4C particles play a significant role in hindering the dislocation movement and limiting the grain boundary slip during tensile deformation, causing an increase in ultimate tensile strength of the annealed composite with bimodal-sized B4C particles at elevated temperatures. The analysis shows that dislocation glide and climb are responsible for the elevated-temperature strengthening mechanism associated with the n-B4C particle addition. For the annealed composites, the ductile fracture of matrix is the primary failure mode at elevated temperatures.

Automated summary

The study shows that nanoscale B4C particles can effectively hinder dislocation movement and limit grain boundary slip in aluminum matrix composites reinforced with bimodal-sized B4C particles, leading to an increase in ultimate tensile strength at elevated temperatures. The primary failure mode at high temperatures is ductile fracture of the matrix in annealed composites.