7A05铝合金激光-MIG复合焊接头组织分析

Analysis of microstructure in 7A05 aluminum alloy welded joints of laser-MIG hybrid welding

采用SEM和TEM对激光-MIG复合工艺焊接的7A05铝合金接头拉伸断口及组织进行了分析。SEM结果表明,室温拉伸断口热影响区为2～5μm的小韧窝,焊核区域为30～50μm的大韧窝,断裂方式为沿晶断裂和少量的解理断裂。TEM分析结果表明,HAZ区域不再存在卵′相,仅仅只有Al_3Zr,说明在激光-MIG焊接的温度场作用下,焊接接头处热影响区出现了明显的η′相的回溶,丧失了η′相的弥散强化作用。

The tensile fracture surfaces and microstructures of 7A05 aluminum alloy joints welded by laser-MIG(metal inert-gas) hybrid welding technology were analyzed by SEM(scanning electron microscopy) and TEM(transmission electron microscopy).SEM results of the room temperature tensile fracture showed that there are small dimples of 2～5μm in the heat affected zone,and big dimples of 30～50μm appear in the weld zone.The fracture mode of the tensile fracture is intergranular fracture and a small amount of cleavage fracture.TEM analysis showed that there is notη'-phase but only Al3Zr in the HAZ no longer.At the thermal effects,the obviousη'-phase dissolution occurs in the heat affected zone,and its dispersion strengthening effect disappears.