Hasnaoui A, Van Swygenhoven H, Derlet P M
Paul Scherrer Institute, CH-5232, Villigen-PSI, Switzerland.
Science. 2003 Jun 6;300(5625):1550-2. doi: 10.1126/science.1084284.
Tensile experiments of fully dense nanocrystalline structures with a mean grain size of less than 100 nanometers demonstrate a considerable increase in hardness but a remarkable drop in elongation-to-failure, indicating brittle behavior. However, dimple structures are often observed at the fracture surface, indicating some type of ductile fracture mechanism. Guided by large-scale atomistic simulations, we propose that these dimple structures result from local shear planes formed around clustered grains that, because of their particular misorientation, cannot participate in the grain boundary accommodation processes necessary to sustain plastic deformation. This raises the expectation that general high-angle grain boundaries are necessary for good ductility.
对平均晶粒尺寸小于100纳米的完全致密纳米晶体结构进行的拉伸实验表明，硬度显著增加，但断裂伸长率显著下降，表明存在脆性。然而，在断裂表面经常观察到韧窝结构，这表明存在某种类型的韧性断裂机制。在大规模原子模拟的指导下，我们提出这些韧窝结构是由聚集晶粒周围形成的局部剪切面导致的，由于这些晶粒的特定取向差，它们无法参与维持塑性变形所需的晶界协调过程。这增加了人们对良好延展性需要一般大角度晶界的期望。
