铝镁异种合金FSW接头形貌及金属间化合物研究

Study on Morphology and Intermetallic Compounds of Aluminum-Magnesium Disimillar Alloy FSW Joint

铝-镁复合结构可以利用两者的优良性能,在装甲外壳、飞机机身等工件中有较大的应用潜力。搅拌摩擦焊(FSW)能有效地避免气孔、夹渣等缺陷,对于异种焊接有较大的优势。但在铝镁异种合金搅拌摩擦焊过程中,焊接接头容易产生硬脆的铝镁金属间化合物,严重恶化焊接接头的力学性能。研究了工艺参数对3 mm厚5A06铝合金和AZ31B镁合金FSW接头焊缝成形的影响,得到成形良好的焊缝焊接工艺参数区间。观察焊缝横截面,分为5个区域,分别是Mg侧的热影响区、Mg侧的热机影响区、搅拌区、Al侧的热影响区、Al侧的热机影响区。并利用SEM和XRD分析发现,铝镁异种合金FSW金属间化合物主要为Al_(3)Mg_(2)和Al_(12)Mg_(17),断裂大多发生在Mg侧,在Mg侧的热机影响区与搅拌区交界处产生了较多的Al_(12)Mg_(17),是造成断裂的主要原因。

The aluminum-magnesium composite structure can take advantage of excellent properties of the both,and has huge application potential in workpieces such as armor shells and aircraft fuselages.Friction stir welding (FSW) can effectively avoid defects such as porosity and slag inclusion,and has great advantages for dissimilar welding.However,in the process of friction stir welding of dissimilar aluminum-magnesium alloys,the welded joint is prone to produce hard and brittle aluminum-magnesium intermetallic compounds,which seriously deteriorates the mechanical properties of the welded joint.The influence of process parameters on the weld forming of 3 mm thick 5A06 aluminum alloy and AZ31B magnesium alloy FSW joint was studied,and the range of welding process parameters with good weld seam were obtained.By observing the cross-section of the weld,divide it into 5 areas,namely the heat affected zone at the Mg side,the thermal mechanical heat affected zone at the Mg side,the stirring zone,the heat affected zone at the Al side,and the heat affected zone at the Al side.And using SEM and XRD analysis,it is found that the intermetallic compounds of aluminum-magnesium dissimilar alloy FSW are mainly Al_(3)Mg_(2) and Al_(12)Mg_(17).Most of the fracture occurs at the Mg side.At the junction of thermal mechanical heat affected zone and the stirring zone at the Mg side,lots of Al_(12)Mg_(17)phase is produced,which is the main cause of fracture.