Liu Jialin, Huang Zaiwang, Pan Zhiliang, Wei Qiuming, Li Xiaodong, Qi Yue
Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing 48824, USA.
State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan Province 410083, People's Republic of China.
Phys Rev Lett. 2017 Mar 10;118(10):105501. doi: 10.1103/PhysRevLett.118.105501. Epub 2017 Mar 9.
Deformation twinning rarely occurs in mineral materials which typically show brittle fracture. Surprisingly, it has recently been observed in the biomineral aragonite phase in nacre under high rate impact loading. In this Letter, the twinning tendency and the competition between fracture and deformation twinning were revealed by first principles calculations. The ratio of the unstable stacking fault energy and the stacking fault energy in orthorhombic aragonite is hitherto the highest in a broad range of metallic and oxide materials. The underlining physics for this high ratio is the multineighbor shared ionic bonds and the unique relaxation process during sliding in the aragonite structure. Overall, the unique deformation twining along with other highly coordinated deformation mechanisms synergistically work in the hierarchical structure of nacre, leading to the remarkable strengthening and toughening of nacre upon dynamic loading, and thus protecting the mother-of-pearl from predatory attacks.
变形孪晶很少出现在通常表现出脆性断裂的矿物材料中。令人惊讶的是，最近在高速冲击载荷下珍珠母中的生物矿物文石相中观察到了变形孪晶。在本快报中，通过第一性原理计算揭示了孪晶倾向以及断裂与变形孪晶之间的竞争关系。在广泛的金属和氧化物材料中，正交文石中不稳定堆垛层错能与堆垛层错能的比值迄今是最高的。这种高比值的潜在物理原因是多邻域共享离子键以及文石结构滑动过程中独特的弛豫过程。总体而言，独特的变形孪晶与其他高度协同的变形机制在珍珠母的层级结构中协同作用，使得珍珠母在动态载荷下具有显著的强化和增韧效果，从而保护珍珠母免受掠食性攻击。
