Anisotropy of Mechanical Properties in a Hot-Pressed Boron Carbide

Effects of microstructure and material properties on the mechanical behavior of hot-pressed boron carbide are presented. The microstructure and intrinsic microstructural inhomogeneities have been characterized using scanning electron microscopy characterization techniques (SEM/EDS/EBSD). In situ mechanical characterizations of the boron carbide microstructure and its larger inhomogeneities have been performed by nanoindentation. Macroscopic dynamic and quasi-static compressive responses have been studied in two characteristic orientations (parallel and perpendicular to the hot-pressing direction) using a modified compression Kolsky bar setup (strain rates of 102−103/s) and standard MTS test machine (strain rates of 10−4−10−3/s). The microstructure characterization showed that boron carbide has a fine-grained microstructure with a complex superposition of nonmetallic inclusions, such as free carbon, AlN, and BN. Nanoindentation tests conducted in three principal planes of the plate revealed an anisotropy of the mechanical properties. The compression tests revealed that the strength of this hot-pressed boron carbide is orientation dependent. Detailed SEM analysis indicated transgranular fracture and microcracking originating at large carbon inclusions. Influences of microstructural anisotropy on the mechanical response of the material are discussed.