- 學位論文
冷加工與加氫水化學對具動態應變時效之鎳基合金於模擬沸水式反應器冷卻水環境之影響研究
Effect of cold work on DSA behavior of Inconel 600 alloy in simulated BWR coolant environment with hydrogen water chemistry
摘要
由前期的研究顯示出冷加工過後的合金 600在攝氏 200 度模擬 BWR 水質的飽和空氣水環境下具有藍脆(Blue brittleness)效應。藍脆為動態應變時效(Dynamic strain aging，簡稱DSA)的特徵之一。藍脆現象的出現，表示金屬材料會提前頸縮，為機械性質上的劣化行為。所以得知動態應變時效如何影響不同冷加工量合金 600的機械性質為重要研究方向。本研究主要進一步探討合金 600在模擬 BWR 加氫水化學(Hydrogen water chemistry, 簡稱HWC)水質環境下的動態應變時效特性和機械性質的影響。利用在加氫水化學的水質環境下慢速拉伸試驗(Slow strain rate tensile, 簡稱SSRT)，可以得到應力應變曲線圖(Stress-strain curve diagram)，以用來判斷機械性質。故本研究目標在以應力-應變曲線來探討加氫水化學中氫在動態應變時效現象中扮演了何種角色，與飽和空氣水環境中進行拉伸是否具有不同的劣化機制。為了能準確判斷動態應變時效中差排和溶質原子交互作用的影響，採用一組單軸拉伸冷加工去做塑性變形來確保試片加工量的均勻性。用慢速拉伸試驗以應變速率10-6/s，來觀察加氫水環路的影響。再改變不同的冷加工量和溫度，來觀察動態應變時效影響合金 600機械性質行為。在HWC下, 已經發現機械性質會有已下幾種現象: 藍脆、有D型態的鋸齒流應力、在單軸拉伸冷加工的試片發生了應變局部化促發破裂現象和在攝氏 300度下有最低的截面積縮減率。
並列摘要
In previous research, the phenomenon of blue brittleness occurred on the cold-rolled Alloy 600 tensile test in simulated BWR air-saturated coolant environments at 200℃. Blue brittleness is the manifestation of dynamic strain ageing (DSA). When blue brittleness of metal occurred, Alloy 600 would be necking early which indicated degradation of mechanical properties. The objectives of this study are to understand the characteristics of DSA observed on Alloy 600 under simulated BWR coolant environments with hydrogen water chemistry (HWC) and its influence on mechanical properties. Stress-strain curves were obtained from the slow strain rate tensile (SSRT) test to evaluate mechanical properties. Cold work by uniaxial tension can produce specimens with uniform plastic deformation, by which the interaction of solute atoms with dislocations can be studied when DSA occurred. Effects of HWC on DSA can be understood from tensile test of different amount of cold work and temperature at a strain rate of 10-6/s. The effect of mechanical properties in HWC were investigated, such as: Blue brittleness, the type D serrations, the intense strain-localization-induced fracture for cold-worked specimens by uniaxial tension and the minimum value of reduction of area at 300℃.