Effect of Welding Speed on Microstructure and Mechanical Properties of Friction Stir Welded Joint of Dissimilar Magnesium/Aluminum Alloys
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摘要: 在不同焊接速度（23.5，47.5，75.0 mm·min-1）下采用搅拌摩擦焊技术对AZ31镁合金和6061铝合金进行对接焊，研究了焊接速度对接头显微组织和力学性能的影响。结果表明：不同速度焊接后，接头焊核区存在条带状组织，焊核区晶粒发生细化；在前进侧焊核区/热机影响区界面处生成了少量金属间化合物Al3Mg2和Al12Mg17；随着焊接速度的降低，各区域的晶粒尺寸有所增大，材料混合均匀程度有所增强；随着焊接速度的增大，后退侧不同区域的硬度均先降后增，前进侧的硬度整体呈增大趋势，接头的抗拉强度和屈服强度均有所下降；拉伸断裂均发生在接头前进侧焊核区/热机影响区界面处，断裂模式均为脆性断裂。Abstract: AZ31 magnesium alloy and 6061 aluminum alloy were butt welded by friction stir welding at different welding speeds (23.5, 47.5, 75.0 mm·min-1). The effects of welding speed on the microstructure and mechanical properties of the joint were investigated. The results show that stripped structures existed in the nugget zone of the joints welded at different speeds. The grains in nugget zone were refined. A small amount of Al3Mg2 and Al12Mg17 metallic compounds formed at interfaces between nugget zone and thermomechanically affected zone on advancing side. With decreasing welding speed, the grain size and the material mixing uniformity in different zones both increased slightly. With increasing welding speed, the hardness in different zones on retreating side decreased first and then increased, while that on advancing side showed an increase trend; the tesile strength and yield strength of the joint both decreased. The joint fractured at the interface between nugget zone and thermomechanically affected zone on advancing side. The fracture mode was brittle.
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