本論文使用分子動力學(Molecular Dynamics, MD)的EAM模型模擬奈米鐵和鎢線之機械行為。並分析其拉伸與壓縮狀態下的原子尺度之變形機制，探討不同結晶方向、材料長度與不同應變率下的強度與塑變行為。針對不同晶體結構(BCC、FCC)的結晶方向(晶面效應)與彈性係數對應變率的影響加以分析比較。
模擬結果顯示，BCC晶體結構的<100>和<110>結晶方向拉伸過程中，奈米鎢線在彈性變形時，會發生彈性波傳現象，導致應力曲線呈現鋸齒狀般形貌；而奈米鐵線則無此現象，拉伸至降伏時，以差排形式直接發射至材料內部。而在<100>結晶方向上，奈米鐵和鎢線易誘發差排糾結，而形成加工硬化的現象；<110>結晶方向的奈米鐵及鎢線則無此現象產生，但降伏應力遠高於<100>結晶方向。奈米線頸縮破斷前，已失去原有BCC晶體結構，並以原子間鍵結直接拉斷為主要模式。
BCC晶體結構的壓縮變形，<100>結晶方向的奈米鐵和鎢線容易發生"挫曲"行為，較長的奈米線產生"挫曲"現象的力量比短的奈米線低；<110>結晶方向的奈米鐵和鎢線會有雙晶變形的產生，雙晶變形引發的原子排列方向轉換會導致流動應力的下降，並且<100>與<110>結晶方向，壓縮應變率越高，降伏應力則越高。降伏應力對應變率的敏感度，拉伸變形中，針對<100>結晶方向(含BCC及FCC晶體)，奈米鎢線為最高；然而，在<110>結晶方向(含BCC及FCC晶體)則奈米鎳線最高。壓縮變形中，針對<100>結晶方向(含BCC及FCC晶體)以奈米鎳線最高；但在<110>結晶方向(含BCC及FCC晶體)，奈米銅線為最高。

This study analyzes mechanical properties and deformation behaviors of iron and tungsten nanowires with uniaxial loading states (tension and compression), orientations、length and different strain rates by molecular dynamics (MD) of the EAM model. Additionally, in the different crystal structures (BCC、FCC), crystal orientations (effects of crystal face) and the elasticity modulus of strain rate are compared.
Results show that during the tensile process, the propagation of elastic wave are obviously observed in <100> and <110> orientations for BCC crystal structure when tungsten nanowires are in the elastic deformation range, leading to zigzag stress curves; However this phenomenon is not observed for iron nanowires. When reaching to yielding tensile stress, dislocations are directly emitted into the material. In <100> crystal orientation, dislocation tangles are easily induced for iron and tungsten nanowires forming of work hardening phenomenon; However, it is not happened in <110> crystal orientation of yet the yield stress is far higher than in <100> crystal orientation. BCC crystal structure has been changed before the fracture of nanowires necking, and the primary failure mode is directly atomic bonding breakage.
When at BCC crystal structure compression deformation, "buckling" behaviors are prone to in <100> crystal orientation for iron and tungsten nanowires, and longer nanowires have smaller "buckling" forces; there is twinning deformation in <110> crystal orientation, leading to the decrease of the flow stress caused by the atomic rearrangement. In <100> and <110> crystal orientations, higher compressive strain rate has higher yielding stress. In tensile deformation tungsten nanowires have the highest strain rate sensitivity of yielding stress, in the <100> crystal orientation (including BCC and FCC crystals); However, nickel nanowires do so in <110> crystal orientation (including BCC and FCC crystals). In compressive deformation, nickel nanowires have the highest strain rate sensitivity of yielding stress in <100> crystal orientation (including BCC and FCC crystals); copper nanowires do so in <110> crystal orientation (including BCC and FCC crystals).

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