Metal matrix composites (MMCs) are composite materials artificially combined with metals and their alloys as the matrix and one or more metal or non-metal reinforcing phases. Most of its reinforcing materials are inorganic non-metals, such as ceramics, carbon, graphite and boron, etc., and metal wires can also be used. It forms modern composite material systems together with polymer matrix composites, ceramic matrix composites and carbon/carbon composites. Boron carbide, also known as black diamond, is an inorganic substance with the chemical formula B₄C, usually a gray-black micropowder. It is one of the three hardest known materials (after diamond and cubic boron nitride) and is used in tank armor, body armor and many industrial applications. It has a Mohs hardness of about 9.5. The advantages of both metal and ceramic can be obtained by combining boron carbide ceramics in metals.
