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

Microstructure evolution of 15wt% boron carbide particle reinforced aluminum matrix composites (B 4 C/Al composites) with titanium addition during liquid-stirring process was dynamically characterized in this paper. B 4 C particles were rapidly dispersed under the mechanical stirring. Many B 4 C clusters were formed in the melt before 20min, but gradually scattered in matrix beyond 20min, owing to further reactive wetting through interface reaction in addition to stirring. After rapid improvement, distribution uniformity slowly approached to completely uniform distribution during 20-55min, even better than random distribution at 55min. Interface reaction produced Al 3 BC, TiB 2 , and AlB 2 by B 4 C erosion and Al 3 Ti decomposition; however, AlB 2 only precipitated in matrix after long time stirring. The growth of TiB 2 transformed from a fine layer to discretely coarse crystals on the B 4 C surface. Reaction mechanism and relationship between reactive wetting and particle dispersion were discussed.