Li Jun, Liu Lisheng, Xu Shuang, Zhang Jinyong, Wu Yuanli
Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics, School of Science, Wuhan University of Technology, Wuhan 430070, China.
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
Materials (Basel). 2018 Sep 29;11(10):1861. doi: 10.3390/ma11101861.
The effects of carbon content on the mechanical properties and deformation mechanisms of boron carbides were investigated by first-principles calculations, based on the density functional theory. The B⁻CBC (13.33 at % C) and B C 2 P ⁻CC (28.75 at % C) were studied and then compared with the deformation of regular BC⁻CBC (20.0 at % C). The results show the B C 2 P ⁻CC, which has the lowest carbon content, has the highest strength and hardness as well as the lowest toughness. With the increase of carbon content, the rhombohedral symmetry will be broken and the three-atoms chains will be replaced by diatomic carbon chains. These changes may have an influence on their anisotropic deformation mechanisms. For the B⁻CBC, the destruction of icosahedra without bending three-atom chains causes structural failure for compression along the axis; while for compression along the axis, new B⁻B bonds are formed, causing an unrecoverable deformation; then it is gradually destroyed until full destruction. For the B C 2 P ⁻CC, the anisotropic deformation mechanism is not obvious. For both loading directions, the breakage of B⁻C bonds causes the stress to drop, suggesting that the structure is beginning to be destroyed. Finally, the icosahedra are fully destroyed, resulting in structural failure.
基于密度泛函理论，通过第一性原理计算研究了碳含量对碳化硼力学性能和变形机制的影响。研究了B⁻CBC（碳含量为13.33 at%）和B C 2 P⁻CC（碳含量为28.75 at%），并与常规BC⁻CBC（碳含量为20.0 at%）的变形进行了比较。结果表明，碳含量最低的B C 2 P⁻CC具有最高的强度和硬度以及最低的韧性。随着碳含量的增加，菱面体对称性将被打破，三原子链将被双原子碳链取代。这些变化可能会对其各向异性变形机制产生影响。对于B⁻CBC，二十面体的破坏而不弯曲三原子链会导致沿轴压缩时结构失效；而沿轴压缩时，会形成新的B⁻B键，导致不可恢复的变形；然后逐渐被破坏直至完全破坏。对于B C 2 P⁻CC，各向异性变形机制不明显。对于两个加载方向，B⁻C键的断裂都会导致应力下降，表明结构开始被破坏。最后，二十面体被完全破坏，导致结构失效。
