摘要：2xxx系與7xxx系航空鋁合金被認(rèn)為采用傳統(tǒng)焊接無(wú)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(jié)省成本，攪拌摩擦焊（Friction Stir Welding-FSW）整體結(jié)構(gòu)被認(rèn)為是未來(lái)航空結(jié)構(gòu)構(gòu)型之一。針對(duì)異質(zhì)2024T3和7075T6兩種航空鋁合金FSW焊接接頭的殘余應(yīng)力分布、力學(xué)性能及疲勞裂紋擴(kuò)展性能，本文進(jìn)行了深入研究。首先采用適當(dāng)?shù)暮附訁?shù)焊接了2024&7075異質(zhì)薄板。焊后采用X-射線衍射法對(duì)四種典型焊件進(jìn)行了殘余應(yīng)力測(cè)試，得到了異質(zhì)焊件內(nèi)的殘余應(yīng)力分布。對(duì)于異質(zhì)焊件，其內(nèi)部殘余應(yīng)力分布無(wú)明顯的雙峰特征，焊縫兩側(cè)的殘余應(yīng)力分布并不對(duì)稱。2024側(cè)的殘余應(yīng)力值浮動(dòng)較大，7075側(cè)的殘余應(yīng)力值浮動(dòng)較小，且主要為拉伸殘余應(yīng)力。然后根據(jù)相關(guān)標(biāo)準(zhǔn)，設(shè)計(jì)出兩種不同的力學(xué)性能測(cè)試試驗(yàn)件，并對(duì)兩種材料的異質(zhì)接頭進(jìn)行了力學(xué)性能試驗(yàn)，得到了焊縫區(qū)域沿焊縫方向與垂直于焊縫方向材料的應(yīng)力應(yīng)變曲線，對(duì)比分析了斷口形貌特征。異質(zhì)接頭焊縫區(qū)兩個(gè)方向材料的應(yīng)力應(yīng)變性能介于兩種同質(zhì)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(jī)影響區(qū)。為研究異質(zhì)FSW焊接薄板的疲勞裂紋擴(kuò)展特性，設(shè)計(jì)出不同試樣進(jìn)行了疲勞裂紋擴(kuò)展試驗(yàn)，并進(jìn)行了裂紋擴(kuò)展速率（FCGR）對(duì)比分析。分析了殘余應(yīng)力對(duì)焊接試樣疲勞裂紋擴(kuò)展速率的影響，并對(duì)疲勞斷裂后的斷口進(jìn)行了SEM電鏡觀察分析，總結(jié)異質(zhì)攪拌摩擦焊接接頭的斷口特性。為兩種航空鋁合金的異質(zhì)攪拌摩擦焊接結(jié)構(gòu)的力學(xué)特性及疲勞性能評(píng)估奠定了基礎(chǔ)。

　　關(guān)鍵詞：攪拌摩擦焊，航空鋁合金異質(zhì)焊接，殘余應(yīng)力，應(yīng)力應(yīng)變曲線，疲勞裂紋擴(kuò)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(lián)系方式

　　馬玉娥：ma.yu.e@nwpu.edu.cn

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