銅鋁鈹形狀記憶合金之再成核相研究

Study of the Re-nucleated Phase of Cu-Al-Be Shape Memory Alloy

林建州(Chien-Chou Lin)

指導教授 ： 王文雄

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.02346

摘要

本論文以真空石英膠囊熔配三種鋁含量在共析成份附近之Cu-Al-Be形狀記憶合金，藉由添加不同之鈹含量，以探討鈹含量對合金共析溫度、序化結構轉變溫度之影響。並進行由固溶溫度直接淬火於序化結構轉變溫度區間內之短時間時效，以分析母相再成核相之晶體結構及顯微組織。最後對時效處理後之試片熱循環後，觀察其形狀回復率變化，以評估經細化麻田散體熱處理後之合金實用性。
實驗結果顯示，鈹含量可有效降低Cu-Al亞共析合金之共析溫度，擴大β單相區；而鈹含量對序化結構轉變溫度並無明顯影響。自β單相區直接鹽浴淬火於序化結構轉變溫度區間進行短時間之時效，可觀察到再成核相生成。再成核相於TEM觀察中，發現再成核相位置中未逆變態回母相之麻田散體為18R結構；而已逆變態之再成核相位置則為D03母相結構，顯示再成核相為D03母相結構。然再成核相其化學成份和D03母相略有差異，可由SEM之背向散射影像觀察出兩者具有不同之對比。在序化結構轉變溫度區間進行短時間時效即會析出α相，α相對形狀記憶效應有不良的影響。經細化麻田散體熱處理及熱循環後之Cu-Al-Be形狀記憶合金，其形狀回復率仍隨熱循環次數增加而下降，顯示其實用價值不高。

關鍵字

鈹含量 ； 共析溫度 ； 序化結構轉變 ； 再成核相 ； 熱循環 ； 形狀回復率

並列摘要

In this thesis, three kinds of Cu-Al-Be shape memory alloys (SMAs) with Al content near the eutectoid composition were melted down and homogenized in evacuated quartz capsules. The effects of Be content on eutectoid temperature and on order-disorder transition temperature were be discussed. And proceed salt-bath quenching from the solution treatment temperature to the order-disorder transition range and short time aging, to analyze the crystal structure and microstructure of the re-nucleated parent phase. Finally, observing the shape memory recovery change after aging and thermal cycling to evaluate the Cu-Al-Be SMA within fine martensite workability.
The results show that Be addition can effectively lower the eutectoid temperature of the hypoeutectoid Cu-Al alloy, but has no effect for the order-disorder transition. The re-nucleated parent phase can be observed by TEM after heat treatment. The martensite, which doesn’t reversely transform to parent phase, at the re-nucleated phase site has the 18R crystal structure; but the parent phase at the re-nucleated phase site has the D03 crystal structure. However, the chemical composition of re-nucleated phase is slightly different from D03 phase which can be observed by SEM back scattering electron image. Short time aging at order-disorder transition temperature will precipitate α phase, which isn’t favored to shape memory effect (SME). After 250 thermal cycles, the shape recovery of Cu-Al-Be SMA within fine martensite is deteriorative gradually which implies that it cannot be applied practically.

並列關鍵字

Be concentration ； eutectoid temperature ； order-disorder transition ； re-nucleated phase ； thermal cycling ； shape recovery

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