Effect of reinforcement content and aging treatment on microstructure and mechanical behavior of B4Cp/6061Al composites

The effects of B4C particle (B4Cp) content and aging treatment on the microstructure and mechanical behavior of B4Cp/6061Al composites prepared by powder metallurgy were investigated. The results demonstrated that the relative density of the B4Cp/6061Al composites decreased slightly by increasing reinforcement content from 0 to 15 wt%. No obvious pores or reaction products were observed at the B4Cp/matrix interfaces by transmission electron microscopy, suggesting that a good, clean interface was achieved. Mg2Si precipitates and dislocations were detected both near the interfaces and in the matrix. Moreover, the aging kinetics could be significantly accelerated by the presence of B4C particles; this behavior was associated with the enhanced dislocation density. The variation in hardness and electrical conductivity as a function of aging time in composites with various B4Cp contents was examined. For the peak-aged composites with increasing B4Cp content from 0 to 15 wt%, the ultimate tensile strength increased from 342.2 to 451.0 MPa, whereas the failure strain decreased from 18.4% to 7.9%. The grain refinement, dislocation strengthening, and work hardening, which contributed to the improvement in yield strength, were theoretically calculated, and the results agreed well with the experimental results.