本文主要是利用霍普金森高速撞擊試驗機及加熱裝置，來探討Ti-29Nb-13Ta-4.6Zr生醫鈦合金在不同溫度及高應變速率荷載下之塑性變形行為及微觀結構分析。分別於實驗溫度25°C、500°C、750°C及應變速率2500s-1、3500s-1、5000 s-1條件下，進行高速撞擊實驗，藉以分析材料在塑變行為中巨觀機械性質變化，再利用(OM、TEM)對微觀結構進行分析，以了解應變速率及溫度對材料塑性變形行為與微觀結構的影響；並由構成方程式來描述巨觀及微觀之關係。
實驗結果顯示，Ti-29Nb-13Ta-4.6Zr在相同溫度下，其塑流應力值、加工硬化率、及應變速率敏感性係數、溫度敏感性係數及理論溫升量，皆隨應變速率上升而上升；而當應變速率固定時，塑流應力值、加工硬化率、及應變速率敏感性係數、溫度敏感性係數及理論溫升量，皆隨溫度值上升而下降。而熱活化體積與活化能，在固定溫度下，則隨應變速率上升而下降；而在應變速率固定下，則隨溫度上升而上升。而各條件下之塑變行為皆可利用Zerilli-Armstrong構成方程式進行模擬，並可作為工程模擬分析時之應用。
在光學顯微鏡(OM)之金相觀察中，可發現本材料為純β相之鈦合金，且在25°C，5000 s-1之條件下可發現絕熱剪切帶之形成與晶粒組織形貌之改變；在穿透式電子顯微鏡(TEM)觀察下，可發現差排密度隨著應變速率上升而上升，隨著溫度下降而下降，此外，隨著應變速率的上升，可以觀測到差排環的產生。最後結合巨觀與微觀之結果顯示，Bailey-Hirsch方程式可準確描述塑流應力值與差排密度之關係。
關鍵字：Ti-29Nb-13Ta-4.6Zr合金、霍普金森桿、高溫、高應變速率、絕熱剪切帶、差排

SUMMARY
In this study, dynamic impact response and microstructural evolution of Ti-29Nb-13Ta-4.6Zr biomedical alloy under high strain rates, ranging from 2500s-1 to 5000s-1 and various temperatures of 25°C, 500°C, and 750°C were investigated by using split-Hopkinson pressure bar.
The results show that the mechanical properties of Ti-29Nb-13Ta-4.6Zr are strongly affected by strain rate and temperature. For instance, for a given temperature, the flow stress, work hardening rate, strain rate sensitivity, temperature sensitivity, and theoretical temperature rise all increase with the increasing strain rate, but decrease with the increasing temperature. However, the thermal activation volume and the activation energy turn out to have the exact opposite result. The Zerilli-Armstrong constitutive law can be used to precisely describe the deformation behavior of Ti-29Nb-13Ta-4.6Zr under different strain rates and temperatures.
The optical microstructure shows that Ti-29Nb-13Ta-4.6Zr has a pure β type titanium alloy as expected. In addition, adiabatic shear band can be observed at high strain rate of 5000s-1 and 25°C. The transmission electron microscopic observations show that the dislocation density increases with the increasing strain rate or the decreasing temperature. Moreover, dislocation cells can be observed as strain rate is higher than 2500s-1. The relationship between the dislocation density and the flow stress can be described by using Bailey-Hirsch equation.
Key words: Ti-29Nb-13Ta-4.6Zr, Hopkinson bar, high temperature, high strain rate, dislocation density

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