铝/钢铆接辅助搅拌摩擦焊搭接接头组织与力学性能分析

Analysis of Microstructure and Mechanical Properties of Aluminum/Steel Riveting Assisted Friction Stir Welding Lap Joints

目的利用搅拌摩擦焊技术对4mm以上厚度的铝/钢板材进行搭接焊接时,容易出现沿厚度方向温度梯度变化大、工艺窗口急剧变窄等问题,难以获得高质量的焊接接头。针对以上问题,采用铆接辅助搅拌摩擦焊的方法,以提高4mm以上厚度铝/钢板材搭接接头的力学性能。方法采用铆接辅助搅拌摩擦焊的方法实现了7mm厚6061铝合金板和8mm厚Q345钢板的搭接;研究了下压量对接头焊核晶粒尺寸、抗剪切力和显微硬度的影响,并分析了接头界面显微组织。结果随着下压量的增大,各接头焊核晶粒尺寸均呈现先减小后增大的趋势,其中矩形槽焊核晶粒尺寸由11.1μm减小至9.6μm后又增大至12.7μm,不开槽焊核晶粒尺寸由11.7μm减小至10.2μm后又增大至12.4μm。金属间化合物(IMC)层厚度随下压量的增大而增大,接头抗剪切力呈先增大后减小的趋势,当下压量为0.3mm时,矩形槽接头和不开槽接头抗剪切力均达到最大值,分别为17600N和15700N,并且在下压量为0.3mm时矩形槽接头和不开槽接头焊核区平均显微硬度均达到最大值,分别为81.1HV和76.8HV。结论在焊接速度为100mm/min、搅拌头转速为600r/min、轴肩下压量为0.3 mm时,利用铆接辅助搅拌摩擦焊可以提高搭接接头的力学性能,能够有效解决以往4mm以上厚度板材搭接接头力学性能较差的难题。

When aluminum/steel plate with a thickness of 4 mm or more is lap-welded,it is difficult to obtain high quality welded joints due to problems such as large temperature gradient changes along the thickness direction and sharp narrowing of the process window.The work aims to adopt the method of riveting assisted friction stir welding to improve the mechanical properties of lap joints of aluminum/steel plates with a thickness of more than 4 mm.The 7 mm thick 6061 aluminum alloy plate and 8 mm thick Q345 steel plate were lapped by riveting auxiliary friction stir welding.The effects of the plunge depth on the grain size,shear resistance and microhardness of the weld nuggets were studied,and the microstructure of the joint interface was analyzed.With the increase of the plunge depth,the grain size of each joint nugget decreased firstly and then increased.The grain size of the rectangular groove nugget decreased from 11.1μm to 9.6μm and then increased to 12.7μm,while the grain size of the non-groove nugget decreased from 11.7μm to 10.2μm and then increased to 12.4μm.The thickness of the intermet-allic compound(IMC)layer increased with the increase of the plunge depth,and the shear force of the joint increased firstly and then decreased.When the plunge depth was 0.3 mm,the shear force of the rectangular groove joint and the non-slotted joint reached the maximum value of 17600 N and 15700 N,respectively.When the plunge depth was 0.3 mm,the average micro-hardness of the weld nugget zone of the rectangular groove joint and the non-slotted joint reached the maximum value of 81.1HV and 76.8HV,respectively.When the welding parameters are welding speed of 100 mm/min,stirring head speed of 600 r/min and plunge depth of 0.3 mm,the mechanical properties of lap joints can be improved by riveting assisted friction stir welding,and the mechanical properties of lap joints of plates with a thickness of more than 4 mm can be effectively improved.