热电耦合对铝/钢连续驱动摩擦焊接头组织的影响机理

采用连续驱动摩擦焊技术焊接纯铝1060/Q235低碳钢异质接头，开展两个周期(30天/60天)热电耦合实验(静载392 N+高温300 ℃+直流60 A)，研究热电耦合对铝/钢异质接头焊缝微观组织、力学性能及界面生长的影响。结果表明：原始态接头界面径向金属间化合物(IMCs)层厚度不均匀，中心区域无明显IMCs生成。热电耦合30天后界面中心生成宽度为0.3~0.5 μm且以颗粒状由钢侧向铝侧弥散分布的IMCs层，整体拉伸断裂在铝母材的热力影响区。热电耦合60天后IMCs层与钢侧之间出现腐蚀沟槽，IMCs破碎，钢侧无裂纹产生，铝侧形成大量由IMCs层向铝母材内部扩展的裂纹和孔洞，焊缝及裂纹尖端处成分偏析，整体拉伸断裂在焊缝处。界面腐蚀和失效速率与界面IMCs层的厚度成正比，即v_center＜v_1/2R＜v_2/3R。由于原始态接头界面组织不均匀以及热电耦合实验过程中界面不同位置组织生长速率的差异，使得热电耦合后接头界面2/3R位置出现不同断裂形貌的分界线，2/3R内侧以准解理断裂方式为主，2/3R外侧为韧窝断裂和准解理断裂的综合结果。

Influence mechanism of thermoelectric coupling on microstructure of aluminum/steel continuous drive friction welding j oints

Continuous drive friction welding technology was used to weld pure aluminum 1060/Q235 low carbon steel dissimilar material joints, and two cycles (30 d/60 d) thermoelectric coupling test (static load 392 N +high temperature 300 ℃+DC 60 A) was carried out. The effect of thermoelectric coupling on the microstructure, mechanical properties and interface growth of the welded joints of aluminum/steel dissimilar materials was studied. The results show that the thickness of the intermetallic compounds (IMCs) layer in the radial direction of the original joint interface is uneven, and there is no obvious IMCs formation in the central area. After 30 days of thermoelectric coupling, an IMCs layer with a width of 0.3-0.5 μm at the center of the interface is formed and dispersed from the steel side to the aluminum side in granular form, the overall tensile fracture is in the thermally affected zone of the aluminum base metal. After 60 days of thermoelectric coupling, a corrosion groove appears between the IMCs layer and the steel side, and the IMCs are broken, there are no cracks on the steel side, a large number of cracks and voids from the IMCs layer to the aluminum base metal are formed on the aluminum side, segregation of components occurs at the weld and crack tip, the overall tensile fracture is at the weld. The speed of interfacial corrosion and failure rate is proportional to the thickness of the interface IMCs layer, namely v_center < v_1/2R < v_2/3R. Due to the uneven structure of the original joint interface and the difference in the growth rate of the structure at different positions of the interface during the thermoelectric coupling test, the boundary line of different fracture morphologies appears at the 2/3R position of the joint interface after thermoelectric coupling. The inner side of 2/3R is dominated by quasi-cleavage fracture, and the outer side of 2/3R is the combined result of dimple fracture and quasi-cleavage fracture.