Lin Yao, Han Luyi, Wang Guangchun
Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061, China.
Materials (Basel). 2023 Apr 3;16(7):2853. doi: 10.3390/ma16072853.
This study investigated the relationship between the Σ3 boundaries, dislocation slip, and plasticity in pure nickel wires after grain boundary (GB) modification. Both quasi in situ tensile tests and simulations were employed. During plastic deformation, twins surrounded by Σ3 boundaries may exhibit a good deformation coordination. With an increase in strain, the slip systems corresponding to the maximum Schmid factor and the actual activated slip systems remain unchanged. Even sub-grains can maintain the dominant slip system of their origin matrix grains. Slip systems with slip planes (111) and (1-1-1) are the most active. Moreover, random boundaries have strong hindering effects on dislocations, and the nearby stress accumulates continuously with an increase in strain. In contrast, Σ3 boundaries demonstrate weak blocking effects and can release the nearby stress due to their unique interfacial structures, which is favorable for improving plasticity. They are more penetrable for dislocations or may react with the piled dislocations. In addition, some Σ3 boundaries can improve their geometrical compatibility factor with an increase in the strain, which enhances the deformation coordination of the grains. The research results provide a better understanding of the plasticizing mechanism for face-centered cubic (fcc) materials after grain boundary modification.
本研究调查了晶界（GB）改性后纯镍丝中Σ3 晶界、位错滑移和塑性之间的关系。采用了准原位拉伸试验和模拟方法。在塑性变形过程中，被Σ3 晶界包围的孪晶可能表现出良好的变形协调性。随着应变增加，对应最大施密德因子的滑移系和实际激活的滑移系保持不变。甚至亚晶粒也能保持其原始基体晶粒的主导滑移系。具有滑移面（111）和（1-1-1）的滑移系最为活跃。此外，随机晶界对位错有很强的阻碍作用，随着应变增加，附近应力持续积累。相比之下，Σ3 晶界表现出较弱的阻碍作用，由于其独特的界面结构能够释放附近应力，这有利于提高塑性。它们对位错更具穿透性，或者可能与堆积的位错发生反应。此外，一些Σ3 晶界会随着应变增加提高其几何相容性因子，从而增强晶粒的变形协调性。研究结果有助于更好地理解面心立方（fcc）材料晶界改性后的增塑机制。
