本文係以利用霍普金森高速撞擊試驗機及加熱裝置，來探討Ti-12Mo-6Zr-2Fe第三代生醫鈦合金在不同溫度與高應變速率荷載下之塑性變形之行為與微觀結構之分析。分別於實驗溫度25°C、450°C、900°C及應變速率1000s-1、2000s-1、3000 s-1條件下，進行高速撞擊實驗，藉此分析材料在進行塑變行為中之巨觀機械性質變化，再利用(OM、TEM)對微觀結構進行分析，了解應變速率及溫度對材料塑性變形行為與微觀結構之影響；最後再藉由構成方程式來描述巨觀及微觀之間的關係。
根據實驗結果顯示，Ti-12Mo-6Zr-2Fe於相同溫度下，其塑流應力值、應變速率敏感性係數、加工硬化率、及溫度敏感性係數與理論溫升量，皆隨應變速率上升而上升；而當應變速率固定時，其塑流應力值、應變速率敏感性係數、加工硬化率、溫度敏感性係數與理論溫升量，皆隨溫度的上升而下降。反觀熱活化體積與活化能，在固定溫度條件下，其值隨應變速率上升而下降；在固定應變速率之下，則隨溫度上升而上升。最後各實驗條件下之塑變行為皆可使用Zerilli-Armstrong構成方程式進行模擬，並可作為往後工程模擬分析時之應用。
在微觀方面本次實驗使用光學顯微鏡(OM)對金相進行觀察，可發現本材料為介穩態之Beta相鈦合金，加熱至Beta轉換溫度(754°C)後可藉由快速冷卻之方法保持純Beta相，但在持續的加熱過程中將出現alpha相與omega相之相結合結構；而在穿透式電子顯微鏡(TEM)觀察下，可發現其差排密度隨著應變速率上升而上升，隨著溫度下降而下降。最後結合巨觀與微觀之結果顯示，Bailey-Hirsch方程式可描述塑流應力值與差排密度兩者之間的關係，透過穿透式電子顯微鏡的觀測，材料在遭受撞擊後差排會糾結在一起，因此差排密度將隨著應變速率的上升而增加，此外隨著應變速率的上升，甚至可觀察到差排環的產生。

In this study, Ti-12Mo-6Zr-2Fe was tested under different strain rates ranging from 1000s-1 to 3000s-1 and different temperatures of 25°C, 450°C, and 900°C by using split-Hopkinson pressure bar. The Aim is to investigate its dynamic impact response and microstructural evolution.
The experimental results reveal that strain rates, strain and temperature affect the mechanical properties of Ti-12Mo-6Zr-2Fe alloy strongly. The Zerilli-Armstrong constitutive law can be used to perfectly describe the deformation behave of this material under different strain rates, strains, and temperatures. Moreover, the flow stress, strain rate sensitivity, work hardening rate, theoretical temperature rise, and temperature sensitivity all increase with increasing strain rate, but decrease with increasing temperature. However, the activation energy and the thermal activation volume is found to decrease with increasing strain rate and increase with increasing temperature.
The optical microstructure shows that Ti-12Mo-6Zr-2Fe has a pure β type at room temperature. However with the increasing temperature it transfers into Hcp type. Above β transfer temperature(754°C), a pure β type appears. The transmission electron microscopic observations reveal that the dislocation density increases with the decreasing temperature or the increasing strain rate. The relationship between the stress and the dislocation density can be expressed by using Bailey-Hirsch equation.

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