本研究在175℃，以 10^-5/s的應變速率對先進高強度鋼 (Advanced High Strength Steel, AHSS)進行低應變量的拉伸試驗，並藉由背向散射電子繞射 (Electron Backscattered Diffraction, EBSD)及穿透式電子顯微鏡 (Transmission Electron Microscope, TEM)分析鋼材變形初期所生成之應變誘發變韌鐵組織及其與母相沃斯田鐵之晶向關係。在次微米沃斯田鐵晶粒生成之 應變誘發變韌鐵一共有四種可能的成核點，分別為沃斯田鐵晶界、已生成之變韌鐵子單元尖端附近、沃斯田鐵/麻田散鐵之相界及雙晶界，且其與母相沃斯田鐵之晶向關係會隨著兩相的介面位置不同而有所差異。應變誘發變韌鐵的形貌應屬於片狀 (plate)，而變韌鐵的sheaf結構與其傾向採用的晶向關係有著密切的關聯。長/寬比較大的變韌鐵傾向採用最密堆積面平行的晶向關係；而長/寬比較小的變韌鐵有較大的機會符合最密堆積方向平行的晶向關係。

In this study, a tensile test was performed on advanced high strength steel (AHSS) at 175 under a strain rate of 10 5/s. The microstructural and crystallographic characterization of strain induced bainitic transformation (SIBT) at the early stage of deformation were carried out by using electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). In submicron grained austenite, there are four possible nucleation sites for SIBT, namely, austenite grain boundaries, near the tip of existing bainite sub units, athermal martensite/austenite phase boundaries and twin boundaries. It was found that the orientation relationship between strain induced bainite and parent austenite often deviated from the well known orientation relationship between FCC and BCC, and this deviation varied with the position of the phase boundaries. The morphology of the strain induced bainite is most likely to be plate like. The orientation relationship between deformation induced bainite and its parent austenite has great influence on its sheaf structure. Deformation induced bainite with a larger aspect ratio tends to adopt the orientation relationship having the close packed plane parallel to the close packed plane of its parent austenite, and bainite with a smaller aspect ratio has a higher probability of having the orientation relationship with the close packed direction parallel to the close packed direction of its parent austenite.

論文審定書 i
中文摘要 ii
Abstract iii
目錄 iv
圖目錄 vi
表目錄 xix
一、前言 1
二、文獻回顧 2
2-1 變韌鐵 2
2-1-1 變韌鐵相變化機制 2
2-1-2 變韌鐵成核與成長 3
2-1-3 變韌鐵的形貌 4
2-2 變形誘發變韌鐵 5
2-2-1 應力對變韌鐵相變化之影響 6
2-2-2 預變形之沃斯田鐵對變韌鐵相變化的影響 7
2-2-3 應變誘發變韌鐵 10
2-3 BCC結構與FCC結構之晶向關係 19
三、研究目的 22
四、實驗方法 23
4-1 實驗材料 23
4-2 拉伸試驗 23
4-2-1 拉伸前表面處理 23
4-2-2 恆溫拉伸 23
4-3 顯微組織分析 24
4-3-1 掃描式電子顯微鏡(SEM) 24
4-3-2 穿透式電子顯微鏡(TEM) 24
4-4 X光能量散佈光譜儀(Energy Dispersive Spectrometers, EDS)分析 25
4-5 背向散射電子繞射(EBSD) 25
五、實驗結果 26
5-1 SEM之顯微組織分析 26
5-1-1 拉伸前之顯微組織觀察 26
5-1-2 應變誘發變韌鐵的分佈情形 26
5-1-3 EBSD分析 28
5-1-4 應變誘發麻田散鐵 30
5-2 TEM之顯微組織分析 31
5-2-1 Deformation twin 31
5-2-2 Athermal麻田散鐵 32
5-2-3 應變誘發變韌鐵的成核及其與母相沃斯田鐵的晶向關係 34
5-2-4 應變誘發麻田散鐵 39
六、討論 41
6-1 麻田散鐵 42
6-2 應變誘發變韌鐵 46
6-2-1 應變誘發變韌鐵的成核 47
6-2-2 晶向關係 49
七、結論 53
八、參考文獻 54

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