本研究利用霍普金森高速撞擊試驗機，探討316L不銹鋼在不同溫度及應變速率之撞擊特性與微觀結構，測試時試片溫度設定在25~800℃，而應變速率則控制在103 s-1至5×103 s-1之範圍內，以分析及瞭解溫度及應變速率在塑變行為及微觀結構上之效應。實驗結果顯示，316L不銹鋼之塑流應力值、加工硬化率、應變速率敏感性係數及熱活化體積皆會隨著應變量、應變速率和溫度範圍之變異而改變。固定溫度條件時，塑流應力值、加工硬化率以及應變速率敏感性係數皆會隨應變速率增加而增益，而熱活化體積則會下降。另一方面，固定應變速率時，塑流應力值、加工硬化率與應變速率敏感性係數會循溫度上升而變小，但是熱活化體積卻會增大。此外，經由實驗結果之驗證，316L不銹鋼之撞擊變形行為可藉由Zerilli-Armstrong構成方程式提供精確之預測。光學顯微鏡之微觀結構分析可發現試片中滑移帶分佈，會隨應變速率與溫度增加而分佈愈廣，也可發現剪切帶裡會有微空孔出現，藉由空孔聚集連結成裂縫，最後造成材料發生破壞；另外，由掃描式電子顯微鏡得知其破壞模式，會延著最大剪應力方向同時發生延性剪切破壞與節瘤狀組織。而穿透式電子顯微鏡觀察則顯示材料中之差排密度、雙晶數量以及 麻田散鐵含量會隨著應變速率上升而增加，但隨著溫度的上升而減少。

This study investigates the impact mechanical properties and microstructure of 316L stainless steel under strain rates ranging from 103 s-1 to 5×103 s-1 at temperatures of 25℃ to 800℃ by using split Hopkinson pressure bar tester. The relationship between mechanical properties and microstructure of the deformed specimen are discussed in terms of testing temperatures and strain rate. The experimental results indicate that the flow stress, work hardening rate, strain rate sensitivity and activation volume of 316L stainless steel all depend significantly on the strain, strain rate and testing temperature. For a constant temperature, the flow stress, work hardening rate and strain rate sensitivity increase with increasing strain rate, while the activation volume decreases. Conversely, for a constant strain rate, the flow stress, work hardening rate and strain rate sensitivity decrease with increasing temperature, while the activation volume increases. It is found that the impact deformation behaviour of 316L stainless steel can be accurately described using the Zerilli-Armstrong constitutive equation. Optical microscopy analyses reveal that slip bands within the grains are found to increase with increasing the strain rate and testing temperature. Microvoid nucleation and growth within shear band are evident during the fracture process. Scanning electron microscopy fractographic observations show that the fracture features are characterized by ductile shear fracture and that knobbly structure form with respect to the direction of maximum shear stress. Transmission electron microscopy structural observation shows that an increase of strain rate or a decrease of testing temperature leads to an increase of dislocation densities, twin densities, and the volume fraction of α’ martensite.

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