(天津大學(xué) 材料科學(xué)與工程學(xué)院 天津市現(xiàn)代連接技術(shù)重點(diǎn)實(shí)驗(yàn)室，天津 300072)
摘 要: 采用攪拌摩擦焊對5 mm厚2024/7075異種高強(qiáng)鋁合金進(jìn)行上下板交換位置的搭接焊試驗(yàn)，分析接頭的缺陷特征和拉伸性能。結(jié)果表明：材料位置和焊接速度對缺陷和拉伸性能有較大影響。當(dāng)2024鋁合金為上板時，接頭中存在大面積孔洞缺陷，焊縫表面粗糙，尤其在300 mm/min焊速下存在較嚴(yán)重的起皮缺陷；鉤狀缺陷為搭接接頭的典型缺陷，低焊速(50和150 mm/min)下鉤狀缺陷向上擴(kuò)展距離較大，7075鋁合金為上板時高焊速(225和300 mm/min)下后退側(cè)鉤狀缺陷水平向焊核區(qū)擴(kuò)展距離較大；在低焊速下，7075鋁合金為上板的接頭強(qiáng)度較高；在高焊速下，2024鋁合金為上板的接頭強(qiáng)度較高；鉤狀缺陷嚴(yán)重減小接頭的有效板厚和有效搭接寬度，是接頭強(qiáng)度降低的主要因素，優(yōu)化攪拌摩擦焊搭接工藝必須同時增大有效板厚和有效搭接寬度。
關(guān)鍵字: 2024/7075鋁合金；攪拌摩擦焊；搭接接頭；缺陷；拉伸性能
（Tianjin Key Laboratory of Advanced Joining Technology, School of Materials Science and Engineering,
Tianjin University, Tianjin 300072, China）
Abstract:Lap joints of 5 mm-thick dissimilar 2024/7075 aluminum alloys were fabricated by friction stir welding (FSW) with changing the top and bottom sheet material position. The defect features and tensile properties of the joints were compared and analyzed. The results show that the defects and tensile properties are significantly affected by material position and welding speed. When 2024 alloy is placed as the top sheet, extensive void defects are found in the joints, the weld surface is coarse and severe peeling defect appears at 300 mm/min especially. As a typical defect in the lap joints, hook extends a large distance upwards at low welding speeds (50,150 mm/min). At high welding speeds (225, 300 mm/min), the retreating side hook propagates largely into the stir zone horizontally when 7075 alloy acts as the top sheet. At low welding speeds, the joint strength is higher when 7075 alloy acts as the top sheet. While the joint shows higher strength at high welding speeds when 2024 alloy is placed as the top sheet. The hook defect reduces the effective sheet thickness (EST) and effective lap width (ELW) of joints severely, which is the main factor reducing the joint strength. So, the EST as well as the ELW should be increased simultaneously to optimize the friction stir lap welding process.
Key words: 2024/7075 aluminum alloy; friction stir welding; lap joint; defect; tensile property
