State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.
Phys Rev Lett. 2009 Nov 13;103(20):205504. doi: 10.1103/PhysRevLett.103.205504.
Low strain hardening has hitherto been considered an intrinsic behavior for most nanocrystalline (NC) metals, due to their perceived inability to accumulate dislocations. In this Letter, we show strong strain hardening in NC nickel with a grain size of approximately 20 nm under large plastic strains. Contrary to common belief, we have observed significant dislocation accumulation in the grain interior. This is enabled primarily by Lomer-Cottrell locks, which pin the lock-forming dislocations and obstruct dislocation motion. These observations may help with developing strong and ductile NC metals and alloys.
低应变硬化迄今为止被认为是大多数纳米晶（NC）金属的固有行为，因为它们被认为无法积累位错。在这封信中，我们展示了在大塑性应变下晶粒尺寸约为 20nm 的 NC 镍的强应变硬化。与普遍的看法相反，我们在晶粒内部观察到了明显的位错积累。这主要是通过 Lomer-Cottrell 锁来实现的，Lomer-Cottrell 锁固定形成位错并阻碍位错运动。这些观察结果可能有助于开发高强度和高延展性的 NC 金属和合金。
