Unité Matériaux et Transformations, CNRS UMR8207, Bât. C6, Université de Lille 1 , Villeneuve d'Ascq 59655, France.
ACS Appl Mater Interfaces. 2017 Jan 18;9(2):1496-1506. doi: 10.1021/acsami.6b13107. Epub 2017 Jan 6.
Nanoscale defects such as dislocations have a profound impact on the physics of crystalline materials. Understanding and characterizing the motion of screw dislocation and its corresponding effects on the mechanical properties of complex low-symmetry materials has long been a challenge. Herein, we focus on triclinic tobermorite, as a model system and a crystalline analogue of layered hydrated cement, and report for the first time how the motion of screw dislocation can influence the strengthening-toughening relationship, imparting brittle-to-ductile transitions. By applying shear loading in tobermorite systems with single and dipole screw dislocations, we observe dislocation jogs around the dislocation core, which increases the yield shear stress and the work-of-fracture when the dislocation lines are along the [100] and [010] directions. Our results demonstrate that the dislocation core acts as a bottleneck for the initial straight gliding to induce intralaminar gliding, which consequently leads to a significant improvement in the mechanical properties. Together, the fundamental knowledge gained in this work on the role of the motion of the dislocation core on the mechanical properties provides an improved understanding of deformation mechanisms in cementitious materials and other complex layered systems, providing new hypotheses and design guidelines for the development of strong, ductile, and tough materials.
纳米级缺陷，如位错，对晶体材料的物理性质有着深远的影响。长期以来，理解和描述螺位错的运动及其对复杂低对称材料力学性能的影响一直是一个挑战。在此，我们专注于三方钙沸石，作为一个模型体系和层状水合水泥的晶体类似物，并首次报道了螺位错的运动如何影响强化-增韧关系，赋予脆性-延性转变。通过在具有单螺位错和偶极螺位错的钙沸石体系中施加剪切载荷，我们观察到位错线在[100]和[010]方向时，在位错核周围出现位错扭结，从而增加屈服剪切应力和断裂功。我们的结果表明，位错核作为初始直滑移的瓶颈，诱导层间滑移，从而显著提高了力学性能。总之，这项工作对位错核运动对力学性能的作用的基本认识，为水泥基材料和其他复杂层状体系的变形机制提供了更深入的理解，为开发强韧、韧性和坚韧的材料提供了新的假设和设计指导。
