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.

Manufacturing Methodology on Casting-Based Aluminium Matrix Composites: Systematic Review

“…Results display a linear improvement of the ultimate tensile strength, microhardness and macrohardness for every particle amount. This is in agreement with other published work [94,129,138,139], as authors use either K 2 TiF 6 flux or Al-Ti-B master alloys to promote the interfacial Ti compounds in B 4 C particles surface. Other fluxes such as Cryolite (Na 3 AlF 6 ) [78,140] and others are employed to improve casting quality and efficiency rather than particle wettability or distribution.…”

“…The presented techniques have an impact on particle wetting and sample microstructure which cannot be evaluated as isolated variables. The assessment of a uniform distribution is carried out by qualitative visual inspection of the microstructure [69,84,85], material property enhancement [77,92,93], particle image analysis regarding distribution along with agglomeration [88,89,94] and hardness profile along a specific axis [95]. Given the low wettability of ceramic particles [96,97], metallic coatings or oxidation of the interface is often performed before the reinforcement is introduced in the melt to improve reinforcement-matrix bonding.…”

“…Zheng et al have studied the effect of stirring time in the microstructure and dispersion of B 4 C-reinforced aluminium with the use of a Ti additive [94]. The authors report that introduction of the Ti in melt promotes the growth of Al 3 Ti films in the surface of the particle, thus, limiting the erosion reactions within a 5 min stirring time.…”

“…Numerical results were later validated empirically for stirring speed, being concluded that the best distribution was achieved for 1000 rpm promoting particle cluster deagglomeration. Li et al has studied the effect of the dynamically liquid-stirring periods on the resulting microstructures, and particles dispersion [94]. The authors show that the shearing and turbulent melt flow is capable of deagglomeration and dispersing B 4 C particles to sufficient state for 20 min, but a fully randomised dispersion was observed at 55 min.…”

Synthesis of boron carbide reinforced aluminum castings through mechanical stir casting

“…10,11 Other methods to fabricate MMC’s include rheocasting, thixocasting, and liquid stir casting strategies. 8,12,13 The proposed solution uses liquid stir casting as a low cost and scalable process for the fabrication of a borated aluminum alloy for use in dry casks. 13…”