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  • 學位論文

真空中熱壓製作TiNi記憶合金薄片

A Possibility Study of Fabricating TiNi SMA Foils with the Vacuum Hot-Pressing Process

指導教授 : 胡塵滌

摘要


本研究屬於製程開發,目標是要在真空中施壓於鎳/鈦/鎳三明治狀疊合箔片同時進行熱處理,以不同熱處理條件研究反應過程,最終預期可以製作出TiNi記憶合金薄片成品,可以避免TiNi合金鑄錠輥壓製作薄片成品製程中加工硬化速率高的困難。研究工作主要分為四部分: 第一部分將本實驗室前期學姐原採用鈦/鎳/鈦三明治狀疊合順序之試片改變為鎳/鈦/鎳順序之試片,從熱處理後試片之OM金相觀察,試片的兩側面皆不再殘留有304SS襯料。證實試片之疊合順序採取鎳/鈦/鎳後能有效改善襯料焊合難以剝除分離的問題。 第二部分將鎳箔片先在熱處理製程前進行冷滾壓,造成鎳箔片內部具有各種高濃度缺陷,比較後發現試片[1373K/0.5min-C+L]之TiNi相厚度較試片[1373K/0.5min-A+L]中TiNi相厚度為薄,證實鎳箔片中的缺陷不能幫助鎳原子擴散進入鈦層中。對於鈦原子擴散進入鎳層方面,由兩試片中原鈦/鎳界面上TiNi3層厚度比較發現試片[1373K/0.5min-C+L]中TiNi3厚度較為厚,證實鎳箔片內部缺陷可以幫助鈦原子擴散進入鎳層中,雖然TiNi3相形成位置為原鈦/鎳界面。 第三部份比較試片在真空中加熱(1373 K)時間的長(4分鐘)或短(0.5分鐘)之效應。發現鎳原子進入鈦層首先快速將所有鈦反應形成Ti2Ni相(少於0.5分鐘);更多鎳原子進入鈦層後,近等原子比的TiNi相藉由非均勻成核自鈦/鎳層界面向試片內側成長。熱處理時間較短時可以觀察到殘餘Ti2Ni相位在兩側TiNi相區的中央,熱處理時間較長時殘餘Ti2Ni相逐漸完全形成TiNi相,更多的鎳原子進入後會在TiNi相中以均勻成核方式形成針狀(Script)的新相(可能為TiNi3相)。 第四部份是形狀記憶效應測試,各種熱處理條件中以試片[1373K/0.5min-A+L]和[1373K/1.5min-A+XL]形狀記憶效應為最佳。試片[1373K/0.5min-A+L]的TiNi相體積百分比為所有試片中最大;而大面積試片[1373K/1.5min-A+XL]因為已完全剝除一側面之鎳層,在缺少一面鎳層拘束下而呈現較好的形狀記憶效果,且該試片經過十次升降溫測試後的形狀記憶效應反而提升,經過五十次測試後仍維持著良好的形狀記憶效果。

並列摘要


The aim of present study is developing a new and simple process to fabricate the TiNi shape memory alloy thin plate by hot pressing the sandwich-stacked Ni/Ti/Ni thin foils under a good vacuum condition. The effects of following various hot pressing conditions are examined and discussed in this report : 1. Change stacking sequence of Ni and Ti foils; 2. Employing cold rolled Ni foils; 3. Change external loading forces in hot pressing; 4. Varied length of time in hot pressing process under a fixed temperature; 5. Very large size specimens. The OM(Optical Microscope), SEM(Scanning Electron Microscope), EDS(Energy Dispersive Spectrometer), DSC(Differential Scanning Calorimetry), and the shape recovery behavior studies were conducted on various hot pressed Ni/Ti/Ni stacked specimens to investigate the microstructural changes, phase constituents, physic properties and shape memory property. Results of present study indicate the good shape memory behaviors could be observed from the specimens fabricated by hot pressed Ni/Ti/Ni stacked foils.

參考文獻


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