Tough, ductile boron carbide can help engineer stronger body armor

Boron carbide is an incredibly hard material, but its low fracture toughness and proneness to brittle failure under high pressure limit its application. Previous reports have identified the primary contributor to these unfavorable properties to be amorphous shear bands in the crystal structure that appear upon impact or under pressure. To open the door for more practical applications, the formation of these bands needs to be inhibited to suppress the material’s failure mechanism.

Shen et al. provided a thoughtful perspective of the experimental and theoretical studies that investigated mitigation techniques for avoiding the formation of boron carbide’s amorphous shear bands. In summary, the authors determined the most promising approach for improving the material’s mechanical properties, particularly its ductility, is by grain boundary engineering.

The grain boundaries, which are the interfaces between differently oriented ordered regions, weaken the crystals’ strength and may lead to grain sliding.

After reviewing the existing literature, the authors concluded that the best method for alleviating amorphization is by incorporating additives into the material, which can reduce the grain sizes in the grain boundaries thereby making boron carbide’s more ductile.

“With the enhanced ductility, it is expected that boron carbide can be applied to many industry applications, such as cutting tools, wear-resistant and protective coating, and even body armor,” said author Qi An.

Source: “Mitigating the formation of amorphous shear band in boron carbide,” by Yidi Shen, Jon Fuller, and Qi An, Journal of Applied Physics (2021). The article can be accessed at https://doi.org/10.1063/5.0044526 .