Deformation and amorphization evolution mechanisms in boron-rich boron carbide under quasi-static loading

Abstract

The inhomogeneous collapse of the periodic crystal structure of boron carbide at high values of shear stress leads to amorphization, resulting in loss of strength and toughness. Doping amorphous boron into boron carbide to replace the C atoms in the boron carbide icosahedron is believed to be effective in retarding the amorphization in boron carbide. In this study, boron carbides with stoichiometric amounts of B_4.2C, B_6.1C, and B_8.6C were prepared through hot pressing. Raman spectroscopy was employed for the microstructure characterisation of the amorphization intensity in the indented regions of the three types of boron carbides under multiple quasi-static Vickers loads. Boron-rich boron carbide undergoes lattice expansion in the presence of a solid solution of excessive amounts of boron, forming a plastic region with many plane defects, thereby inhibiting the amorphization of the boron carbide and changing its deformation mechanism. The dislocations and stacking faults that occur in boron-rich boron carbide would promote the formation of extremely narrow linear and sharp type amorphous shear bands, which would inhibit the formation of broad amorphous bands.