Mitigating the formation of amorphous shear band in boron carbide

Atomistic explanation of shear-induced amorphous band formation in boron carbide.

Boron carbide (B4C) is very hard, but its applications are hindered by stress-induced amorphous band formation. To explain this behavior, we used density function theory (Perdew-Burke-Ernzerhof flavor) to examine the response to shear along 11 plausible slip systems. We found that the (0111)/<1101> slip system has the lowest shear strength (consistent with previous experimental studies) and tha...

Nucleation of amorphous shear bands at nanotwins in boron suboxide

The roles of grain boundaries and twin boundaries in mechanical properties are well understood for metals and alloys. However, for covalent solids, their roles in deformation response to applied stress are not established. Here we characterize the nanotwins in boron suboxide (B6O) with twin boundaries along the {0111} planes using both scanning transmission electron microscopy and quantum mecha...

Carbide formation in tungsten-containing amorphous carbon films by annealing

Tungsten-containing amorphous carbon films were produced by dual magnetron sputter deposition. The formation of carbide phases after heat treatment in inert gas at temperatures up to 2800 K was investigated by X-ray diffraction for tungsten concentrations below 25 at%. After deposition, each film consists of an amorphous carbon matrix with atomically dispersed W inclusions. Annealing up to 2800...

Boron carbide/n-silicon carbide heterojunction diodes

Shear Band Formation in Bulk Metallic Glasses

In recent times, there has been a growing interest in the machining of amorphous metallic alloys, which are also called bulk metallic glasses (BMGs). These materials differ from common polycrystalline metallic alloys, because their atoms do not assemble on a crystalline lattice, and as a result, they have unique physical, mechanical, and chemical properties. A number of BMGs have been found to ...