本研究的目標是探討熱處理製程對兩種合金含量的錳矽鋁鋼材的顯微組織與機械性質的影響。其中A鋼材成份為0.16C-2.0Mn-1.0Si-1.2Al，B鋼材成份為0.16C-5.7Mn-1.6Si-1.6Al，主要製程則包含熱軋、熱軋退火、冷軋、冷軋退火與變韌鐵持溫處理。利用掃描式電子顯微鏡、背向散射電子繞射儀與X光繞射儀分析不同製程鋼材的顯微組織，以拉伸試驗量測機械性質，了解製程參數與機械性質之關係，並且探討影響其強度與塑性的機制。
A鋼材經過735 oC-10 hr的熱軋退火處理後命名為AA鋼材，而未經熱軋退火製程則命名為AO鋼材。結果顯示，AA鋼材中γ/M相的Mn含量由退火前的1.9 wt%上升到4.6 wt%，沃斯田鐵體積分率則從2%上升到9%。而B鋼材經過(620 oC、650 oC、680 oC)-10 hr的熱軋板退火處理後，γ/M相中的Mn含量約為12~13 wt%，沃斯田鐵體積分率則分別為15%、25%與29%。證實長時間的熱軋退火製程，可使錳富集到沃斯田鐵相中提升其穩定性。
AO與AA鋼材經冷軋與冷軋退火後，其拉伸曲線均呈現雙相鋼特性，亦即於拉伸時沒有降伏點與降伏延伸現象。其中由於AO鋼材於冷軋退火後，原本在鋼材中分佈較不均勻的γ/M組織，反而得以均勻分佈於肥粒鐵晶界，進而有效的強化鋼材。而AA鋼材在冷軋退火後，γ/M粒徑較大且肥粒鐵內錳含量較低，因此其抗拉強度(800~900 MPa)普遍低於AO鋼材(900~1000 MPa)，而錳富集於沃斯田鐵的程度亦不足以使Ms溫度低於室溫，因此無法進一步提升延性。
B鋼材分別經620 oC、650 oC與680 oC退火後，雖然沃斯田鐵含量具有明顯的差異，但經冷軋退火後卻具有相似的顯微組織與拉伸特性，表示在B鋼材的製程中，其性質由後段溫度較高的冷軋退火所主導。
B鋼材於熱軋退火、冷軋與冷軋退火後，隨退火溫度升高依序呈現超細晶強化、應變誘發塑性、應力誘發塑性與雙相強化的機械性質特徵。當鋼材於660 oC進行退火，由於各相組織細小，鋼材降伏強度極高(1124 MPa)，但延性較差(21.1%)。而鋼材在700 oC與725 oC退火後，在全程應變中，其加工硬化率均可維持在1000 MPa以上，為應變誘發塑性的強化機制，因此具有優異的延伸率(33.6%、29.3%)。鋼材於750 oC退火後，其加工硬化率在降伏延伸後大幅提升至10000 MPa再快速下降，因此延伸率較低(22.3%)，此外降伏強度大幅下降至約700 MPa，推測有少量穩定性較差的沃斯田鐵在變形初期即以應力誘發模式變態。鋼材於775 oC退火後，其拉伸曲線不具有降伏點與降伏延伸現象，但與雙相鋼相比，其加工硬化率明顯較為緩慢的下降，可能為TRIP效應所造成。而鋼材於800 oC退火後，殘留沃斯田鐵僅剩10%，其拉伸曲線不具有降伏點與降伏現象，且加工硬化率曲線與雙相鋼類似。
B8冷軋板經過750 oC-60 sec退火並於460 oC持溫300 sec之試片，其顯微組織與機械性質皆與B8-750近似。因此可知B8冷軋板於兩相區退火後施以變韌鐵相變持溫處理，對於其顯微組織與機械性質皆無明顯的影響。

The study investigated the effect of heat treatments including hot-band annealing (HBA), cold-rolled annealing (CRA), and isothermal bainitic annealing (IBA) on microstructure and mechanical properties of two Mn-Si-Al steels. Steel A contains 0.16 wt%C, 2.0 wt%Mn, 1.0 wt%Si, 1.2 wt%Al, and steel B contains 0.16 wt%C, 5.7 wt%Mn, 1.6 wt%Si, 1.6 wt%Al. The microstructures of the steels were examined by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD), and the mechanical properties of two steels were measured by tensile tests.
The experimental results showed that after hot band annealing (735 oC-10 hr), the volume fraction of retained austenite in steel A increased from 2% to 9%, and the Mn content in the phase of γ/M increased from 1.9 wt% to 4.6 wt%. For steel B, the Mn content of γ/M were around 12 to 13 wt%, and the volume fraction of retained austenite were 15%, 25%, and 29%, when the hot-band were annealed at 620 oC, 650 oC and 680 oC, respectively. It proves that the Mn content and the stability of austenite is increased after a long-time, hot-rolled annealing process.
The stress-strain curves of the AO (without HBA) and AA (with HBA) steels, after cold-rolled and cold-rolled annealing, showed characters of free from yield point and yield-point elongation, which are similar to there of the dual-phase steel. The γ/M in the AO steels distributed uniformly at the grain boundary of ferrite, so it could improve the strength of the steels. The grain size of γ/M in the AA steels was larger and the Mn content of ferrite was lower, so the tensile strength (800~900 MPa) is lower than the AO steels (900~1000 MPa). Since the Mn content of γ/M was not high enough to suppress the Ms temperature below room temperature, no enough austenite could be retained to improve the ductility of the steels.
Steel B showed different mechanical characteristics at various temperatures. After annealed at 660 oC, steel B exhibited a complex phase microstructure and a yield stress of 1124 MPa with an elongation of 21.1%. The high yield ratio character is similar to that of metals strengthened by ultrafined grains. When the steel was annealed at temperature 700 oC or 725 oC, high work hardening rates of 1000 MPa or above can be maintained throughout the whole deformation history. The high work hardening rate was attributed from strain induced martensitic transformation which results in high ductilities of 29-34%. When the annealing temperature was increased to 750 oC, the work hardening rate increased dramatically to a high value of 9600 MPa in the early stage of deformation and then decreased gradually on deformation. A high tensile strength of 1300 MPa and moderate elongation of 22.3% were yield. The rapid increase of work hardening rate indicated that the stability of austenite was low and it transformed to martensite in the early stage of deformation. When the steel was annealed at 775 oC, the yield point and yield point elongation are absent in the stress-strain curve. However, the work hardening rate of the 775 oC-annealed steel decreased less rapidly than that of regular dual-phase steel, indicate that TRIP effect was still active in this sample. When the steel was annealed at 800 oC, it contained 10% austenite. The yield point and yield point elongation were absent in the stress-strain curve, and the work hardening behavior was similar to the dual-phase steel.
No significant change of tensile behavior was observed for steel B which was isothermally hold at 460 oC for 300 sec then annealed at 750 oC for 60 sec, demonstrating that the volume fraction of austenite did not change with the application of IBA.

論文審定書 i
致謝 ii
摘要 iii
Abstract v
總目錄 vii
表目錄 ix
圖目錄 x
第一章、前言 1
第二章、文獻回顧 3
2.1 第一代先進高強度鋼-TRIP鋼製程與機械性質之彙整 3
2.1.1 合金元素之作用 3
2.1.2 兩相區退火 4
2.1.3 變韌鐵相變持溫 5
2.1.4 TRIP鋼材之金相結構 7
2.1.5 熱處理導引成分區隔分佈 8
2.2 麻田散鐵相變化 9
2.2.1 熱滯性麻田散鐵 9
2.2.2 應力及應變誘發麻田散鐵相變態 10
2.2.3 合金元素與Ms、Md之關係 11
2.3 TRIP效應 12
2.4 第三代先進高強度鋼製程與機械性質之彙整 14
2.5 中山大學過去於TRIP鋼材領域之研究 15
第三章、實驗方法 17
3.1 試片準備 17
3.1.1 試片製備流程 17
3.2 顯微組織分析 18
3.2.1 掃描式電子顯微鏡分析 18
3.2.2 X光繞射分析 18
3.2.3 計點法 19
3.3 機械性質分析 19
3.3.1 硬度分析 19
3.3.2 拉伸試驗分析 19
第四章、實驗結果 20
4.1 熱軋板 20
4.1.1 顯微組織分析 20
4.1.2 硬度分析 24
4.2 冷軋板 24
4.2.1 兩相區退火 24
4.2.1.1 機械性質分析 24
4.2.1.2 顯微組織分析 26
4.2.2 變韌鐵相變持溫 30
4.2.2.1 機械性質分析 30
4.2.2.2 顯微組織分析 31
第五章、討論 33
5.1 熱軋板退火 33
5.2 冷軋板退火 34
第六章、結論 40
第七章、參考文獻 42

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