摘要：2xxx系與7xxx系航空鋁合金被認為采用傳統焊接無法焊接的金屬。因能焊接2xxx系與7xxx系鋁合金，并且能減輕重量、提高綜合性能和節省成本，攪拌摩擦焊（Friction Stir Welding-FSW）整體結構被認為是未來航空結構構型之一。針對異質2024T3和7075T6兩種航空鋁合金FSW焊接接頭的殘余應力分布、力學性能及疲勞裂紋擴展性能，本文進行了深入研究。首先采用適當的焊接參數焊接了2024&7075異質薄板。焊后采用X-射線衍射法對四種典型焊件進行了殘余應力測試，得到了異質焊件內的殘余應力分布。對于異質焊件，其內部殘余應力分布無明顯的雙峰特征，焊縫兩側的殘余應力分布并不對稱。2024側的殘余應力值浮動較大，7075側的殘余應力值浮動較小，且主要為拉伸殘余應力。然后根據相關標準，設計出兩種不同的力學性能測試試驗件，并對兩種材料的異質接頭進行了力學性能試驗，得到了焊縫區域沿焊縫方向與垂直于焊縫方向材料的應力應變曲線，對比分析了斷口形貌特征。異質接頭焊縫區兩個方向材料的應力應變性能介于兩種同質焊縫材料之間，拉伸斷口參差不齊，垂直焊縫方向試樣斷裂位置位于焊縫邊界處的熱機影響區。為研究異質FSW焊接薄板的疲勞裂紋擴展特性，設計出不同試樣進行了疲勞裂紋擴展試驗，并進行了裂紋擴展速率（FCGR）對比分析。分析了殘余應力對焊接試樣疲勞裂紋擴展速率的影響，并對疲勞斷裂后的斷口進行了SEM電鏡觀察分析，總結異質攪拌摩擦焊接接頭的斷口特性。為兩種航空鋁合金的異質攪拌摩擦焊接結構的力學特性及疲勞性能評估奠定了基礎。

　　關鍵詞：攪拌摩擦焊，航空鋁合金異質焊接，殘余應力，應力應變曲線，疲勞裂紋擴展速率

Fatigue Property Of Dissimilar Fricition Stir Welded Aluminum Joint For Aircraft Structure^1））
Ma YuE^*,2)，Li Jiang^*，Zhao Zhenqiang^*
*( School of Aeronautics, Northwestern Polytechnical University，Xi’An 710072，China )

　　Abstract:Friction stir welding （FSW） technology can reduce weight,improve the comprehensive performance and save cost,particularly it can weld 2xxx and 7xxx aluminum alloys that can't welded by the tradition welding way, so FSWed integral structure is considered to be one of aeronautical structure in the future. The distribution of residual stress, mechanical properties and fatigue crack growth properties of dissimilar 2024-T3 and 7075-T6 thin friction stir welded plates have been studied in this paper. According to present research results in China and abroad, dissimilar 2024-T3 and 7075-T6 thin plates were welded by proper friction stir welding parameters. And then X-ray diffraction method was used to measure residual stress profiles in welded plates. For dissimilar welded plate, the residual stress doesn't present the 'double peak', and the residual stress in both sides of weld joint is asymmetric. And residual stress in 2024 side has a large fluctuation, while in 7075 side it keeps mainly tensile and has a smaller fluctuation. According to related standards, two different samples were designed. Then mechanical tests of dissimilar welded joints were performed to get the stress-strain curves along and perpendicular to the direction of the weld. Fracture surfaces were studied and compared. For the dissimilar welded samples, the stress-strain curve is between curves of monolithic welded joints, and fracture surface is zigzag. Fracture points of the sample with perpendicular weld are located in the heat affected zone near the border of the weld line. In order to study fatigue crack growth of dissimilar thin welded plates, seven kinds of samples were designed to perform the fatigue crack propagation tests. Fatigue crack growth rates （FCGR） were compared with each other and parent material to analyze the influence of residual stress on fatigue crack growth rate. And SEM was used to analyze the fatigue fracture surfaces. The feature of fracture surfaces was summarized. All results provide useful information for fatigue analysis of FSWed aircraft structure.

　　Key words:Friction stir welding,dissimilar joint of aluminum alloy for aircraft application, residual stress, stress-strain curve, fatigue crack growth rate

　　聯系方式

　　馬玉娥：ma.yu.e@nwpu.edu.cn

責任編輯：趙澤南

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