鎢極氣體保護焊接(Tungsten Inert Gas Welding, TIG)是一種常應用在鋁合金材料間之焊接技術，有操作方便焊接速度快等優點，所以廣泛應用於焊接工業，因為現行商業鋁合金焊條如4043、5356在焊接較高強度工件如6061、7075後，焊道強度與原始被焊接材差距較大，故本實驗設計兩種鋁合金焊條，以評估對應焊道特性。本研究第一部分為探討6069改質之高鎂矽銅型添加鋁合金焊條(MSC)，希望藉由焊條本身較高強度，以及和6XXX系鋁合金較匹配之熱處理條件，以取代現行通用鋁合金焊條，且為了擴展鋁合金焊條應用領域，後續針對其在不同溫度下，以及浸泡食鹽水後進行拉伸性質分析。第二部分為探討改質自鑄造材A356之高矽銅鎂添加型鋁合金(SCM)，因為高矽可以增加其流動性，有利焊接時滲透力，高銅則能達到強化效果，希望能夠應用在較特殊焊接環境，如船級等需要雙邊焊接工件，後續亦針對其在不同溫度下以及浸泡食鹽水後進行拉伸性質分析，並綜合檢討相關材料應用機制。
第一部分實驗結果顯示：鎂矽銅鋁合金焊道(MSC)在經過固溶化及人工時效熱處理後，能夠有效消除焊接熔融後存在之樹枝狀晶，第二強化相亦有效固溶至基地中，使得焊道拉伸強度達到250MPa，超越現行通用鋁合金焊條焊接後焊道強度。
第二部分矽銅鎂鋁合金(SCM)添加之焊道在經過固溶化及人工時效熱處理後，焊接熔融後樹枝狀晶並未完全被消除，可是拉伸強度已超過310MPa，接近原始被焊接之6061基板，後續高溫拉伸機械性質在到達240°C時仍可保有大於200MPa拉伸強度；在浸泡食鹽水實驗中，浸泡七天後亦可維持其強度。
綜合兩部份鎂矽銅鋁合金(MSC)以及矽銅鎂鋁合金(SCM)焊道研究，兩者在焊接後經過固溶化以及人工時效熱處理，拉伸強度皆優於現行通用4043及5356鋁合金，另外，焊道的高溫性質與耐氯阻抗都呈現可用性，相關成果能夠幫助鋁合金焊條之開發應用。

Tungsten inert gas welding(TIG) is a common welding technique used in aluminum alloys. It has advantages such as short operation time, and easy process. However, the tensile strength of commonly used fillers AA5356 and AA4043 don’t match some aluminum alloys like AA6061 and AA7075. The tensile strength in welding bead will decrease by almost 50% after welded with AA5356 or AA4043 fillers. To solve this issue, two kinds of aluminum alloy were used as filler and welded with AA6061 plate in this research.
The first filler is aluminum alloy added with higher Mg, Si, Cu (modified from AA6069). It has better mechanical properties than AA6061. Moreover, after T4/T6 heat treatment (570°C, 0.5 h- 190°C, 6 h), its tensile strength will up to 400 MPa which is higher than filler AA6061. This new filler has potential to replace the commercially used filler. The second filler is aluminum alloy added with higher Si, Cu, Mg (modified from A356). It contains 8.6 wt. % Si and consequently it has high fluidity and low shrinkage in welding applications. After T4/T6 heat treatment (490°C, 6 h- 170°C, 6 h), its tensile strength will reach 370MPa. This new filler can still used in some unique working places like ships because it can weld in double side.
According to the results of the experiments, the welding bead of first filler (with higher Mg, Si, Cu) has 250 MPa in UTS. On the other hand, the welding bead of second filler (with higher Si, Cu, Mg) has up to 310MPa in UTS. Both of them shows better mechanical properties than welding bead made with AA5356 or AA4043. Besides, the second filler remains its tensile strength in 180°C and 240°C. After 7 days in satuated salt water, the UTS can still up to 250MPa.

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