Ceramic-based composites offer many advantages, such as light weight, high strength, high wear and corrosion resistance, high-temperature properties etc, which makes them ideal candidate materials for use in aerospace and defense applications. There have been a number of successful developments of ceramic-based composites for various applications by novel processes, such as, SHS, Lanxide DIMOX process, XD process etc. but not much work has been done on the development of armor-composites by such processes. This research investigates the fabrication of $B_4C$-based composites for armor applications by a novel processing technique called the dipping exothermic reaction process (DERP).
$B_4C$ is an important ceramic material with many useful physical and chemical properties. Among the outstanding physical and mechanical properties of boron carbide is its hardness, which is second to diamond and c-BN. This specific property comes along with other attractive properties such as high impact and wear resistance, low density, high melting point, and excellent resistance to chemical agents as well as high capability for neutron absorption. However, its extreme sensitivity to brittle fracture and the difficulties involved in fabricating dense $B_4C$ materials have limited its use in industrial applications. These problems can be significantly reduced by the production of $B_4C$ -based composites, especially $B_4C$ -metal/intermetallic composites.
In this study, high volume fraction (≥ 30 vol.%) $B_4C$ -reinforced $TiAl_3$ matrix composites have been successfully fabricated by the dipping exothermic reaction process (DERP) from preforms of $B_4C$, aluminium and titanium powders. DERP is carried out in molten aluminium and the processing is very simple and quick (3 minutes), hence composites in near net-shape can be fabricated in a single step. The processing temperature is 900℃ (which is lower than that used in conventional sintering and composite manufacturing processes) and the equipment required for composite fabrication is very simple and easily available.
It has been shown that the final microstructure and properties of the DERP-fabricated $B_4C$ -reinforced TiAl3 matrix composites can be tailored by treatment of the constituent powders prior to preform preparation. This involves separate mixing of Al and Ti powders prior to mixing with $B_4C$ powder, and preform preparation and protective coating of $B_4C$ with $ZrB_2$ and $TiB_2$ prior to mixing with Al and Ti powders, and preform preparation. Post heat-treatment after infiltration proved to be an important processing step to reduce the amount of unreacted aluminium and increase the amount and homogeneity of the ceramic reinforcement, hence enhancing the mechanical properties such as hardness. Composites consisting of $B_4C$, $Al_3BC$ and $TiB_2$ reinforcements have successfully been fabricated by DERP and subsequent heat-treatment.
An effort has been made to explain the infiltration mechanism of molten aluminium into $B_4C$ -Al-Ti powder preforms. Furthermore, based on experimental and thermodynamic data, the phase evolution mechanism during infiltration and after post infiltration heat-treatment has also been suggested.
