Samaee Vahid, Dupraz Maxime, Pardoen Thomas, Van Swygenhoven Helena, Schryvers Dominique, Idrissi Hosni
Electron Microscopy for Materials Science (EMAT), University of Antwerp, Antwerp, Belgium.
Photons for Engineering and Manufacturing, Paul Scherrer Institut, Villigen PSI, Switzerland.
Nat Commun. 2021 Feb 11;12(1):962. doi: 10.1038/s41467-021-21296-z.
The introduction of a well-controlled population of coherent twin boundaries (CTBs) is an attractive route to improve the strength ductility product in face centered cubic (FCC) metals. However, the elementary mechanisms controlling the interaction between single arm dislocation sources (SASs), often present in nanotwinned FCC metals, and CTB are still not well understood. Here, quantitative in-situ transmission electron microscopy (TEM) observations of these mechanisms under tensile loading are performed on submicron Ni bi-crystal. We report that the absorption of curved screw dislocations at the CTB leads to the formation of constriction nodes connecting pairs of twinning dislocations at the CTB plane in agreement with large scale 3D atomistic simulations. The coordinated motion of the twinning dislocation pairs due to the presence of the nodes leads to a unique CTB sliding mechanism, which plays an important role in initiating the fracture process at a CTB ledge. TEM observations of the interactions between non-screw dislocations and the CTB highlight the importance of the synergy between the repulsive force of the CTB and the back stress from SASs when the interactions occur in small volumes.
引入可控的相干孪晶界（CTB）群体是提高面心立方（FCC）金属强度-延展性乘积的一条有吸引力的途径。然而，控制纳米孪晶FCC金属中常见的单臂位错源（SAS）与CTB之间相互作用的基本机制仍未得到很好的理解。在此，对亚微米镍双晶体进行了拉伸加载下这些机制的定量原位透射电子显微镜（TEM）观察。我们报告称，CTB处弯曲螺型位错的吸收导致在CTB平面上形成连接孪生位错对的收缩节点，这与大规模三维原子模拟结果一致。由于节点的存在，孪生位错对的协同运动导致了一种独特的CTB滑动机制，该机制在CTB台阶处引发断裂过程中起着重要作用。非螺型位错与CTB之间相互作用的TEM观察突出了在小体积内发生相互作用时CTB的排斥力与SAS的背应力之间协同作用的重要性。
