Investigation into the use of boron carbide to improve the mechanical properties of composite aluminium alloys

The present work is aimed at obtaining a metal composite material based on Al - 5%Cu aluminium alloy by the addition of B₄C boron carbide and studying the microstructural features and mechanical properties of cast billets based on this material. Aluminium alloy cast billets containing 5%wt. of Cu with a boron carbide content varying from 2-7 wt% were prepared in laboratory die casting machines. Immediately prior to casting, B₄C particles with a size of 5-7 μm were introduced into the melt under continuous stirring. A tensile test of the samples having an elongation of 0.1-0.5 mm was carried out by Shimadzu tensile testing machines in accordance with ASTM standards. The microstructure of the experimental samples was studied by scanning electron microscopy using an INSPECT S50 microscope (FEI, Netherlands). In terms of the aluminium matrix microstructure following the introduction of boron carbide, the composite was established to contain inclusions of the Al₂Cu intermediate crystallisation phase and B₄C particle inclusion matrices distributed throughout the entire sample volume. Porosity zones were detected in the form of weak contact of the matrix material with the embedded surface of the boron carbide reinforced particle. A high level of wetting by the matrix melt was observed, leading to a uniform distribution of particles in the matrix. The best indicators of hardness (113 HV) and tensile strength (~180 MPa) are characteristic of the samples with the addition of boron carbide in an amount of 5%. At this content, due to the low observed particle segregation in the volume of the Al-Cu matrix, a uniform fine-grained billet structure for the selected composition of the alloy was obtained. According to the research results, the composition of the alloy obtained by die casting based on Al-5%Cu alloy with the addition of boron carbide in amount of 5% can be recommended as a suitable material for the manufacture of products with due to its attractive hardness and strength properties.

aluminium matrix composites, scanning electron microscopy, boron carbide, die casting, metal composite materials, mechanical properties