臺灣博碩士論文加值系統

本研究係探討AA7005與AA5080鋁合金，經GTAW與GMAW銲接後，在熱影響區及銲道區之殘留應力分佈對材料抗蝕性之影響。
本研究之工作計分兩部份：一為殘留應力量測，另一為極化曲線量測。所用之銲接方式有同材AA7005鋁擠型方管件之GMAW銲接，及異材AA7005/AA5083之GMAW及GTAW銲接。本研究係依照ASTM E837-96規範於銲件之熱影響區進行殘留應力量測實驗；及依ASTM G5-94規範之要求，進行極化曲線實驗，探討殘留應力值對極化曲線之影響。
實驗結果顯示，AA7005/AA5083異材MIG銲接件之AA5083側Y軸殘留應力高於AA7005側；AA7005/AA5083異材TIG銲接件之AA7005側Y軸殘留應力高於AA5083側，且縮弧端殘留應力值均高於起弧端，且MIG異材銲接件Y軸殘留應力值變化範圍大於TIG異材銲接件。AA7005鋁合金基材在平行擠製方向具有8.6Mpa到19.5Mpa的殘留拉應力，此殘留拉應力再加上Zn及Mg元素的成份差異，為造成AA7005鋁合金基材極化曲線之腐蝕電位差異[由-1.075(V)到-0.824(V)]及腐蝕電流密度差異[由3.98×10-8 (A/cm2)到1.7×10-6 (A/cm2)]之主因。TIG異材銲接件在AA5083側熱影響區材料之極化曲線未顯示鈍化區，而MIG異材銲接件之AA5083側熱影響區材料之極化曲線則呈現一鈍化區，此結果顯示MIG異材銲接件AA5083側熱影響區材料之腐蝕性質有改變。TIG異材銲接件與MIG異材銲接件之AA5083側熱影響區材料其腐蝕電位為-0.98V及 -0.923V均較基材之腐蝕電位為低；其腐蝕電流密度為6.6×10-7A/cm2及3.16×10-6A/cm2均較基材為高，顯示殘留應力可以改變AA5083鋁合金之極化曲線，增加此區域材料原子的活性，形成局部性的伽凡尼電池，導致腐蝕電位的降低，及腐蝕電流密度的提昇。

The objective of this study is to investigate the effect of residual stress, produced by TIG and MIG dissimilar material welding, on the corrosion behavior of AA7005 and AA5083 aluminum alloys. This study contains two parts. The first part is the measurement of the HAZ’s residual stress, in accordance with the ASTM E837-96. The second part is the measurement of polarization curve, in accordance with the ASTM G5-94. Results from both measurement were compared to find a correlation between residual stress and corrosion behavior.
Experimental results showed that the residual stress at HAZ in AA5083 side is higher than that in AA7005 side for MIG dissimilar material welding. But in TIG dissimilar material welding the result is reverse. Shrink end has larger residual stress variation than the start end, and MIG welding process produces higher residual stress variation in direction perpendicular to the weldment than that produced by TIG welding process. AA7005 base metal have tensile residual stress from 8.6Mpa to 19.5Mpa in the direction parallel to extrusion direction. A large variation in polarization curves was observed for the base metal of AA7005 aluminum alloy. The reduction potential (Icorr) is varied from -1.075(V) to —0.824(V), and the corrosion current density (Jcorr) is varied from 3.98×10-8A/cm2 to 1.7×10-6 A/cm2. These residual stresses in accompany with the variations of alloy elements, Zn, Mg, are the major reasons for the large variation of Icorr and Jcorr obtain from the polarization curves of AA7005 base metal.
Polarization curves obtained from materials on AA5083 side HAZ did not showed passivation zone in TIG dissimilar material welding, but passivation zone was observed for materials obtained from AA5083 side HAZ in MIG dissimilar material welding. This result showed that the corrosion behavior of AA5083 side HAZ material was changed after MIG dissimilar material welding. The reduction potential (Icorr) obtained from material on AA5083 side HAZ is —0.98V and —0.923V respectively, those values are much lower than that of base metal. The corrosion current density (Jcorr) on AA5083 side HAZ is 6.6×10-7A/cm2 and 3.16×10-6A/cm2 respectively, those values are much higher than the corrosion current density (Jcorr) of base metal after TIG and MIG dissimilar material welding. This result showed that residual stress may form local galvanic cell and alters the corrosion behavior of AA5083 aluminum alloy, causing a change in polarization curve, decreasing reduction potential and increasing the corrosion current density.

摘 要 I
ABSTRACT III
誌 謝 V
目 錄 VI
圖目錄 IX
表目錄 XI
第1章 前言 1
1-1 背景 1
1-2 目的 2
第2章 理論探討 3
2-1 鋁及鋁合金之特性和分類及銲接性質 3
2-1-1 鋁及鋁合金之特性和分類 3
2-1-2 鋁及鋁合金之銲接性質 5
2-2 鋁合金之銲接方法 6
2-2-1 遮蔽氣體電弧銲 6
2-2-2 惰性氣體金屬電弧銲 8
2-3 殘留應力 9
2-3-1 殘留應力的來源 9
2-3-2 溫度與應力分佈 10
2-3-3 量測殘留應力之方式 11
2-4 腐蝕 12
2-4-1 腐蝕的定義 12
2-4-2 腐蝕的形態 12
2-5 腐蝕的電化學理論 13
2-5-1 極化曲線 14
2-5-2 極化曲線之優點 17
2-5-3 極化曲線之偏差 17
第3章 實驗方法與步驟 19
3-1 實驗材料 20
3-2 實驗設備 21
3-2-1 銲接設備 21
3-2-2 殘留應力設備 23
3-2-3 極化曲線設備 26
3-3 殘留應力量測 27
3-3-1 盲孔鑽孔法之應變量測步驟 28
3-3-2 數據計算及修正 30
3-3-3 應變規黏貼位置 33
3-3-4 鋸削對殘留應力值之影響性 34
3-3-5 量測系統誤差之分析 35
3-4 極化曲線試驗 36
第4章 結果與討論 38
4-1 殘留應力之量測 38
4-1-1 基材之殘留應力 38
4-1-2 同材銲接殘留應力量測 40
4-1-3 異材銲接殘留應力量測結果 42
4-2 極化曲線測定 48
4-2-1 基材(AA7005) 48
4-2-2 基材AA5083 51
4-2-3 AA7005與AA5083之比較 52
4-3 應力對極化曲線之影響 53
4-3-1 熱影響區 53
4-3-2 銲道 61
4-3-3 殘留應力與極化曲線 63
第5章 結論 66
參考文獻 68

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