本文主要是探討7075-T6鋁合金低溫之撞擊特性與微觀結構分析。利用壓縮式霍普金森桿撞擊試驗機(Hopkinson bar)及低溫裝置，分別於應變速率1000 s-1、2000 s-1、3000 s-1和5000s-1及實驗環境溫度-196℃、-100℃、0℃各條件下，進行7075-T6鋁合金之高速撞擊變形，以分析材料在塑變形為中巨觀與微觀結構變化，並導入構成方程式以描述材料之應力應變關係。
實驗結果顯示，7075-T6鋁合金材料機械性質隨溫度和應變速率的不同而有顯著差異。在相同的溫度下，塑流應力值、加工硬化率及應變速率敏感性係數皆隨應變速率增加而上升;然而當固定應變速率時，其塑流應力值、加工硬化率、應變速率敏感性係數則會隨溫度之增加而下降。而熱活化體積則是呈現相反的趨勢。溫度敏感性係數則隨應變速率上升或溫度的降低增加。所有之應力與應變特性可進一步藉由Zerilli-Armstrong構成方程式作準確的描述。
在微觀破斷面之掃描式電子顯微鏡分析上，可觀察到破壞面上具有脆性及延性破壞組織，且隨著溫度的降低及應變速率的提升，脆性破壞的面積愈大。而穿透式電子顯微鏡觀測之結果發現差排密度隨著應變速率上升和溫度降低而增加。另由光學顯微鏡之觀測得知，變形後試片之晶粒尺寸隨著溫度的下降與應變速率的上升而降低，同時在-100℃及3000 s-1荷載下，具明顯的塑流剪切帶。而塑流應力值隨著差排密度的增加及晶粒尺寸的降低有明顯增加的趨勢，其相互間的關聯性可進一步藉由典型之關係式來作定量的說明，其中K值為108.28，而k'=16.09。

The mechanical properties and dislocation substructure of 7075-T6 aluminum alloy deformed at temperatures of 0ºC, -100ºC and -196ºC and strain rates of 1000 s-1, 2000 s-1, 3000 s-1 and 5000 s-1 are investigated using a compressive split-Hopkinson pressure bar. It is found that the flow stress and strain rate sensitivity increase with increasing strain rate, but decrease with increasing temperature. Moreover, the work hardening rate decreases with increasing strain rate and temperature. The temperature sensitivity increases with increasing strain rate or decreasing temperature. However, the activation volume decreases with increasing strain rate or decreasing temperature. Moreover, it is shown that the high strain rate deformation behaviour of 7075-T6 aluminum alloy can be adequately described using the Zerilli-Armstrong constitutive equation. The fracture surfaces of the deformed specimens contain both cleavage structures and dimple-like structures. The cleavage structure increases with increasing strain rate or decreasing temperature. A pronounced adiabatic shearing effect is observed in the specimens deformed at -100ºC and 3000 s-1. Transmission electron microscopy observations reveal that the dislocation density increases with increasing strain rate or decreasing temperature, leading to a greater flow stress. The correlation between the dislocation density, grain size and the flow stress obeys the general relation of , where k and k' are found to have values of 108.28 and 16.09 , respectively for the current 7075-T6 specimens.

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