臺灣博碩士論文加值系統

本研究使用經過均質化處理的6069鋁合金鑄錠，以熱壓縮實驗探討6069鋁合金高溫變形特性以及材料加工性，其熱變形溫度範圍為300 ~ 550 ℃，應變速率範圍為1×10−3~10 s−1，真應變則為0.7。主要使用雙曲線正弦函數(Hyperbolic sine law)計算組合方程式的結構參數，同時觀察變形後試件之顯微結構，以分析熱變形條件對微結構影響。透過製程加工圖以及變形後試件之顯微結構來探討6069鋁合金鑄錠熱變形及加工性的影響。
研究顯示，在6069鋁合金高溫變形時，可以雙曲線正弦函數表示應變速率、溫度及應力之關係。而由組合方程式所得之應力指數n值為5.78、活化能Q值為171kJ/mol。
利用這些壓縮數據製作製程加工圖，用以確定可加工區域。此安全加工區可分為動態回復和動態再結晶。根據金相顯微結構研究顯示，顯微組織的變化和功率消耗效率有關，動態回復發生在功率消耗效率數值約中間的區域，而部份動態再結晶則發生在數值較高的區塊。研究指出，在不穩定區中，不穩定流與局部金屬流有極大的相關性。在應變速率敏感指數m等值圖上顯示，因為m值較低，因此發現有局部金屬流。由再結晶驅動力的角度來觀察，在部份動態再結晶中可以發現，溫度增加，其活化能越低。

The hot workability of homogenized 6069 Al alloy cast ingot was examined via hot compression tests. These tests were conducted using Gleeble-3500 thermal simulation machine within a temperature range of 300 °C to 550 °C and a strain rate range of 0.001 s−1 to 10 s−1. Hyperbolic sine law was used to study the constitutive behavior during hot compression. Optical microscopy analysis was performed to explore the effect of hot deformation conditions on the microstructural changes. By using processing map and microstructure to analyze that the temperature strain rate and homogenization of the high temperature deformation behavior of 6069 Al alloy impacted on the hot deformation and working properties.
In the constitutive analysis, stress multiplier α was treated as constant in the hyperbolic constitutive equation. Constitutive parameters were estimated based on the maximum flow stresses. The obtained stress exponent n and activation energy Q were 5.78 and 171 kJ/mol, respectively.
The compression data were then used to construct a processing map, through which a safe processing region was identified. The safe processing region could be divided into dynamic recovery and dynamic recrystallization domains. The variation in microstructure was related to the variation in efficiency of power dissipation, as indicated by microstructure observations. Dynamic recovery was observed in regions associated with the intermediate efficiency of power dissipation, whereas partial dynamic recrystallization occurred in regions with high efficiency. Flow instability was found to be related to flow localization. The strain rate sensitivity m map showed that flow localization occurred because of the deformation conditions with low m values. The kinetic analysis revealed a decrease in apparent activation energy with increased temperature in the partial dynamic recrystallization region.

摘要 i
ABSTRACT ii
致謝 iv
目錄 v
表目錄 vii
圖目錄 viii
第一章 緒論 1
1-1 前言 1
1-2 研究方法與目的 1
第二章 文獻回顧 2
2-1 基礎性質 2
2-1-1 6069鋁合金相關文獻回顧 2
2-1-2 均質化 3
2-1-3 回復 4
2-1-4 再結晶 5
2-2 組合方程式 6
2-3 製程加工圖 9
2-3-1功率消耗率圖(Efficiency of power dissipation map) 10
2-3-2 不穩定圖(Instability map) 11
2-4 Gleeble 3500型熱加工模擬機 12
第三章 實驗方法與步驟 13
3-1 實驗材料 13
3-2 實驗步驟 13
3-2-1 壓縮實驗 13
3-3 金相顯微結構 14
第四章 結果與討論 15
4-1 流變行為 15
4-2 製程加工圖結果分析 16
4-2-1 功率消耗效率圖(Efficiency of power dissipation map)結果分析 16
4-2-2 不穩定性圖結果 17
4-2-3 製程加工圖結果 17
4-3顯微結構結果分析 18
4-3-1 製程加工圖之顯微結構分析 18
4-3-2 m值分析 20
4-4 動能分析 20
4-4-1 組合關係分析 20
4-4-2 Z值對微結構之影響 22
第五章 結論 25
參考文獻 26

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