【摘要】 为研究不同焊接速度对2A12/7075异种铝合金搅拌摩擦焊（Friction Stir Welding,FSW）接头成形和力学性能的影响,在室温下对焊接接头进行冲击实验和拉伸实验,采用扫描电子显微镜（SEM）和能谱仪（EDS）对断口形貌和成分进行表征分析,采用光学显微镜（OM）对接头横截面进行观察。结果表明,焊接接头呈非对称形,前进侧宽度小于后退侧宽度;焊速为120mm/min时,接头冲击功最高达到18.45J,焊速为140mm/min时抗拉强度最优,为239.68MPa,延伸率为7.56%。随着焊速的增加,焊缝表面起毛倾向减小,出现隧道孔缺陷的倾向增加;接头抗拉强度与塑韧性随焊速的增加而提高,但焊速为140mm/min时,焊核区出现了隧道孔缺陷,造成接头的韧性下降;拉伸断口呈现上部韧性断裂和下部解理断裂,EDS元素分析韧性断裂部分存在第二相粒子Mg₂Si。更多还原

【Abstract】 In order to study the effects of different welding speeds on the forming and mechanical properties of 2A12/7075 dissimilar aluminum alloy Friction Stir Welding（FSW）joints,The impact and tensile tests were carried out d on the welded joints at room temperature using Scanning Electron Microscopy（SEM）and Energy Dispersive Spectrometer（EDS）to characterize the fracture morphology and composition,and the cross section of the joint was observed by Optical Microscope（OM）.The results show that the welded joint is asymmetric,the width of advancing side is smaller than that of the retreating side.The joint impact energy is up to 18.45 Jwhen the welding speed is 120 mm/min,and the tensile strength is the best when the welding speed is 140 mm/min,which is 239.68 MPa and the elongation is 7.56%.With the increase of welding speed,the tendency of peeling on the surface of weld is decreased and the tendency of tunnel hole defects increased.The tensile strength and plasticity of the joint increased with the welding speed increasing.When the welding speed was 140 mm/min,the tunnel hole defect was formed in the nugget zone,which led to the decrease of joint toughness.The tensile fracture showed the upper ductile fracture and lower dissociation fracture.The EDS element analysis show had the second phase particle Mg₂Si in the ductile fracture.更多还原