鋁合金薄板應用摩擦攪拌銲接之研究

此研究利用現有鑽床進行加工，透過自行設計的自動進刀機構，並且安裝自製夾具夾持試片，將該機構固定於鑽床工作台上予以施銲，期許以較低成本進行摩擦攪拌銲接完成接合工作。實驗以三款不同自製攪拌棒(M1、M2、M3)對於1050的1mm薄鋁合金加工，並且藉由鑽床轉速(550RPM、1750RPM及3000RPM)及自動進給速率(30、50、60 mm/min)作為施銲參數。於施銲後進行銲道表面觀察、金相顯微實驗、微硬度試驗、抗拉試驗和掃描式電子顯微鏡分析及量測，瞭解加工後的機械性質。經研究獲得以下幾點結論： 1.M3刀刃因軸肩較小，與母材接觸面積小以至於無足夠摩擦熱，完全無法接合母材；經M2刀刃施銲後的試片，從金相組織觀察其材料融填效果差，抗拉伸強度極低，接合成效不佳；M1刀刃於高轉速抗拉強度有明顯提升，試片1-M1-C3的最大抗拉強度平均值為72.47 MPa，達母材(約120MPa)強度之68%，其次試片1-M1-C2抗拉強度達40.32MPa，所以較佳刀刃為M1。 2.經M1及M2攪拌棒加工後都有擠料、孔洞缺陷及類溝槽狀缺陷現象。以M1攪拌棒施銲之金相顯微組織其呈現類似沙漏狀結構的銲核區；M2攪拌棒施銲後的顯微組織則為長條結構的銲核區樣貌，但無論是何款攪拌棒其銲核區皆為非對稱。轉速低時攪拌較無足夠摩擦熱充填接合斷面；若轉速提高，接合區硬度下降，且硬度低於母材許多，銲核區缺陷也明顯增加，在銲道RS側的擠料問題及熱機影響區、熱影響區也較AS側明顯。 3.施銲試片經拉伸後觀察可發現其破斷面並無像母材一樣出現酒窩狀組織，而是呈現劈裂面，可見其未受到充分塑性變形即破壞，因此拉伸試驗之強度均低於母材；另從各破斷面亦可發現其有組織成長之特徵，顯示在摩擦攪拌銲接過程中，其溫度已達再結晶溫度以上，晶粒有成長之現象。

關鍵字

鋁合金；摩擦攪拌銲接；抗拉強度；摩擦熱；孔洞

並列摘要

In this study, current drilling machine is used for Friction Stir Welding (FSW) of aluminum sheets. In order to have a lower cost for welding through FSW process, a self-designed automatic feeding mechanism is used, and a self-made fixture is set to clamp the work piece. Later, keep the feeding mechanism on the drilling machine for welding. In this experiment, three different stir tools (M1、M2、M3) are used for processing on 1050 1mm aluminum sheets. Also, three different rotating speeds of the welding tool (550, 1750 and 3000 rpm) and three kinds of automatic feeding rates (30、50、60 mm/min) are used as welding parameter. After welding, test the quality of machine through weld pass surface watching, metallographic test, microhardness test, tensile test, and Scanning Electronic Microscope (SEM) analyzing and measuring. Three conclusions of this study are shown below: 1.Because of the thin shoulder of blade M3, there is small contacting area between base metal and blade M3. As the lack of heat of friction, blade M3 cannot connect with base metal; the work piece welding with blade M2 has poor filling result, low tensile strength, and weak connection; M1 blade has a better tensile strength with high rotating speed, and the ultimate tensile strength of work piece 1-M1-C3 is 40.32MPa, which reaches to 68% of tensile strength of base metal (about 120MPa). Tensile strength of the other work piece 1-M1-C2 is 40.32MPa. Therefore, blade M1 is a better option. 2.After processing through stir tool M1and stir tool M2, flash、cavity defect、groove defect phenomenon are presented. Using stir tool M1weld microstructure presents an hourglass shape structure Weld Nugget Zone (WNZ); stir tool M2 presents weld long string shape microstructure WNZ. Nevertheless, their WNZ are all asymmetric no matter which stir tool is used. Low rotating speed has insufficient friction of heat connecting with the cut surface; if the rotating speed is increased, the hardness of the connecting area declines, and the hardness will be much lower then base metal. Also, the defect of WNZ will obviously be increased. The flash problem and the ThermoMechanically Affected zone (TMAZ)、Heat Affected zone (HAZ) of weld pass RS show more clearly than weld pass AS. 3.After stretching, the cut surface of the welding work piece has no dimple structure like base metal. On the contrary, it shows cleavage facet. As the result, the work piece is damaged without enough transformation. Thus, the strength of tensile tests are lower then base metal. In addition, the growth of microstructure can be discovered on each cleavage facet. It represents that during the process of FSW, the grain grows when it reaches the recrystallization temperature.