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研究生:高崇源
論文名稱:時效對Cu-Al-Be形狀記憶合金之影響
指導教授:王文雄王文雄引用關係
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:材料科學與工程學研究所
學門:工程學門
學類:材料工程學類
論文種類:學術論文
論文出版年:1995
畢業學年度:83
語文別:中文
論文頁數:115
中文關鍵詞:形狀記憶合金真空熔配
相關次數:
  • 被引用被引用:5
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  本實驗以真空熔配五種組成在共析成分附近的CuAlBe形狀記憶合金,分別在260℃及400℃進行恆溫時效處理,然後以電阻量測試驗、形狀記憶回復率測試及顯微鏡組織觀察等,來探討析出物對於CuAlBe形狀記憶合金的影響,並以X光繞射(XRD)與穿透式電子顯微鏡(TEM)進行相變化和結構分析等方面的研究。
  實驗結果顯示,CuAlBe形狀記憶合金在恆溫時效過程中,隨時效時間增加,其麻田散體變態溫度的變化,主要是和析出物的形成有關,當析出物溶質成分比共析成分多時,麻田散體變態溫度會隨時效時間增加,往高溫變化,反之,當析出物溶質成分比共析成分少時,麻田散體變態溫度則會往低溫變化;同時因為析出物的生成,將使得溫度遲滯變大,而形狀記憶效應也有明顯降低的趨勢。
  經由掃瞄式電子顯微鏡(SEM)的觀察得知,在400℃恆溫時效過程中,各合金在晶界處會有共析組織產生,而且隨著時效時間的增加,此共析組織會繼續往晶粒內擴展,這將使得參與反應的麻田散體量減少,對材料的形狀記憶效應及機械性質都有不好的影響。
  而從X光繞射及穿透式電子顯微鏡的分析可知,CuAlBe合金之母相為DO3結構的AL19.7BE5.9CU74.4,麻田散體則是屬於18R,其內部組織為疊差(Stacking Fault)。當合金AL含量比共析成分少時,在260℃恆溫時效所產生的析出物為A1-plate,其結構和麻田散體同樣是屬於18R結構,A1-plate的內部組織亦為疊差,而在400℃恆溫時效所生成的析出物,則是屬於A1(FCC)結構的α相;至於合金Al含量比共析成分高時,在400℃恆溫時效處理時,則會有於屬於D8(3)結構的γ2(Al4Cu9)析出。
  In this work, five CuAlBe shape memory alloys with different chemical compositions, aroud eutectoid, were aged at 260℃ and 400℃. The effects of precipitates on the alloys have been studied by an electrical resistance-temperature measurement method, a shape memory recovery test and Scaning Electron Microscopic (SEM) observation X-ray diffraction (XRD) and Transmission Electron Microscopic (TEM) observation were utilized to investigate the phase transformations of the alloys and to analyze the crystal structures of the alloys.
  The results show that the change of martensitic transformation temperature of the CuAlBe alloys with increasing aging time is dependent on the solute content of precipitates. Soute rich precipitate raises the martensitic transformation temperature of the alloys. On the other hand, solute lean precipitate lowers the martensitic transformation temperature of the alloys. In addition, the formations of precipitates extend the temperature hysteresis and reduced the shape memory effect of alloys.
  From SEM observation, when the alloys aged at 400℃, eutectoid structure was found in the grain boundaries, and gradually extended into grain interior with increasing time. These eutectoids lower the shape memory effect and mechanical properties of the alloys.
  From XRD and TEM analysis, the crystal sturcture of parent phase and martensite of the alloys are DO3(AL19.7Be5.9Cu74.4) and 18R, respectively; The sub-structure of the martensite is stacking fault. The precipitate of the alloys with lower A1 content aged at 260℃ is a1-plate, 18R, same structure as martensite; However, the precipitate of these alloys aged at 400℃ is a, which is A1(FCC) structure. For alloys with higher A1 content aged at 400℃, the precipitate is r2(Al4Cu9) with D83 structure.
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