本研究利用霍普金森高速撞擊試驗機，研究 Inconel 718超合金在不同溫度及應變速率之撞擊特性與微觀結構，測試時試片溫度分別設定在-150℃、25℃、300℃和550℃，而應變速率則為1000 /s、3000 /s和5000 /s，以探討溫度及應變速率在塑變行為及微觀結構上之效應；同時利用OM及TEM進行微觀結構的觀察，以解析巨觀特性與微觀結構兩者間之關連性。實驗結果顯示，溫度與應變速率對Inconel 718超合金的機械性質影響甚鉅。在相同溫度條件下，其塑流應力值、加工硬化率與應變速率敏感性係數均會隨應變速率之增加而上升，但熱活化體積會變小。在相同應變速率條件下，其塑流應力值、加工硬化率與應變速率敏感性係數則會隨溫度之增加而下降，不過熱活化體積會變大。另外，藉由Zerilli-Armstrong構成方程式，可精確的描述Inconel 718超合金的塑性變形行為。另由穿透式電子顯微鏡之微觀結構分析，可清楚的觀察到差排密度會隨著應變速率上升而增加，但隨著溫度的上升而減少。而差排密度與塑變應力間之關係可藉由Bailey-Hirsch type關係式來定量描述。光學顯微鏡觀察之結果顯示，Inconel 718超合金晶界的變形程度，隨著應變速率的上升或溫度的下降更加明顯，而晶界變形程度的不同，正是證明材料在不同應變速率及溫度下的微觀結構影響。

This study uses a split-Hopkinson bar to investigate the plastic deformation behavior of Inconel 718 super alloy at the strain rates of 1000 /s, 3000 /s and 5000 /s and the temperatures of -150℃, 25℃, 300℃and 550℃, respectively. Based on the experimental results and microscopic observations, the correlations between mechanical properties and microstructure are established. The experimental results indicate that the effects of temperature and strain rate on mechanical properties of Inconel 718 super alloy are significant. At constant temperature, the flow stress, work hardening rate and strain rate sensitivity increase with increasing strain rate, but the activation volume decreases. For a constant strain rate, the flow stress, work hardening rate and strain rate sensitivity decrease with increasing temperature, but the activation volume increases. Besides, the Zerilli-Armstrong constitutive equation can be used to describe the plastic deformation of Inconel 718 super alloy precisely. Transmission electron microscopy (TEM) observations show that the dislocation density increases with increasing strain rate, but decreases with increasing temperature. The relationship between the dislocation density and flow stress can be described by the Bailey-Hirsch type relation. Optical microscopy (OM) observations reveal that the deformation of grain boundary in Inconel 718 super alloy is found to increase with the enhancement of strain rate and the decrease of temperature. Different deformation of grain boundary proves the influence of microstructure under various strain rates and temperatures.

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