微观组织对高强铝合金接头冲击韧度的影响

Effect of Microstructure on Impact Toughness of High Strength Aluminum Alloy Welds

以2519-T87高强铝合金为研究对象,研究其接头的冲击断裂性能及微观组织。研究表明,晶界上分布的α+θ(CuAl2)共晶相是焊缝中心和熔合线附近区域韧性较差的主要原因,并且由于熔合线附近等轴晶区中的共晶相数量高于焊缝中心区域,导致其成为接头韧性最差的区域。晶界液化以及显微裂纹的产生是部分熔化区脆化的主要原因。析出物的溶解使完全回归区获得接头最大冲击吸收功22J,而析出物的粗化导致过时效区韧性降低,冲击吸收功仅仅只有7J。断口观察发现除了部分熔化区的断口是脆性断口,接头其他区域断口均为韧窝型断口,且完全回归区中的韧窝最深,韧窝内部的析出物最少。

The 2519-T87 high strength aluminum alloy is welded to study the impact properties and microstructure of the joints. Results indicate that the lower impact toughness of weld centre zone and fusion line zone is caused by the network distribution of α＋θ（CuAl2） eutectic phase along the grain boundary. And the higher amount of eutectic phase i s in the equiaxed zone along fusion line, which makes it have the poorest impact toughness. The local melting and microfissure are the main cause for the embrittlement of partially melted zone. The value of the impact absorbed energy in the full-reverted region reaches the maximum 22 J because of the dissolution of precipitates, whereas that value in overaged zone is only 7 J because of coarsening of precipitates. Fractography shows that the fracture of partially melted zone is brittle intergranular fracture, and those of other zones are dimple fractures. The dimples in the fracture of the fully reverted zone are the deepest, and there are least particles in them.