In Situ Observation of Fracture along Twin Boundaries in Boron Carbide
Penghui Li, Yeqiang Bu, Linyan Wang, Chong Wang, Junquan Huang, Ke Tong, Yujun Chen, Julong He, Zhisheng Zhao, Bo Xu, Zhongyuan Liu, Guoying Gao, Anmin Nie, Hongtao Wang, Yongjun Tian
Abstract
Abstract The observation of fracture behaviors in perfect and twinned B 4 C crystals via in situ transmission electron microscopy (TEM) mechanical testing is reported. The crystal structure of the synthesized B 4 C, composed of B 11 C icosahedra connected by boron‐deficient C–▫–C chains in a chemical formula of B 11 C 3 , is determined by state‐of‐the‐art aberration‐corrected scanning TEM. The in situ TEM observations reveal that cracking is preferentially initiated at the twin boundaries (TBs) in B 4 C under both indentation and tension loading. The cracks then propagate along the TBs, thus resulting in the fracture of B 4 C. These results are consistent with the theoretical calculations that show that TBs have a softening effect on B 4 C with amorphous bands preferentially nucleated at the TBs. These findings elucidate the atomic arrangement and the role of planar defects in the failure of B 4 C. Furthermore, they can guide the design of advanced superhard materials via planar defect control.