Microstructure evolution of 15 wt% boron carbide/aluminum composites during liquid-stirring process

Abstract

Microstructure evolution of 15 wt% boron carbide particle reinforced aluminum matrix composites (B₄C/Al composites) with titanium addition during liquid-stirring process was dynamically characterized in this paper. B₄C particles were rapidly dispersed under the mechanical stirring. Many B₄C clusters were formed in the melt before 20 min, but gradually scattered in matrix beyond 20 min, owing to further reactive wetting through interface reaction in addition to stirring. After rapid improvement, distribution uniformity slowly approached to completely uniform distribution during 20–55 min, even better than random distribution at 55 min. Interface reaction produced Al₃BC, TiB₂, and AlB₂ by B₄C erosion and Al₃Ti decomposition; however, AlB₂ only precipitated in matrix after long time stirring. The growth of TiB₂ transformed from a fine layer to discretely coarse crystals on the B₄C surface. Reaction mechanism and relationship between reactive wetting and particle dispersion were discussed.