对一种Al-Zn-Mg-Cu-Mn-Zr-Er合金薄板进行了全自动TIG填丝焊接,观察接头微观组织形貌,并测试其力学性能.结果显示焊缝未出现典型的联生结晶形貌,而是由等轴细晶粒层和大量等轴树枝晶构成,在晶界或枝晶间断续分布复合T (AlZnMgCu)相;焊接热影响区因沉淀相变化,硬度值不同,分为近缝的固溶区和远缝的过时效区,晶粒保持与母材相同的拉长形貌,未见明显长大;接头横截面的显微硬度最低值在焊缝,HV约为1200 MPa,母材显微硬度HV约为1840 MPa,接头抗拉强度为421.75 MPa,达到母材的65.08％,拉伸断裂位置处于焊缝中,断口形貌为典型的韧性断裂,等轴韧窝底部存在破碎的第二相颗粒,其成分与焊缝中复合T相基本一致.
New Al-Zn-Mg-Cu alloy sheets have been welded using automatic TIG welding with filler wires.The microstructure characteristics and mechanical properties of weld joints were analyzed.Results show that the fusion zone (FZ) is comprised of a non-dendritic equiaxed grain zone (EQZ) and a coarser dendritic equiaxed grains,and the fusion boundary does not nucleate epitaxially from the heat affected zone (HAZ) substrate,and the compound T (AlZnMgCu) phase precipitates discretely on grain boundaries.The HAZ is divided into a solid solution zone that is close to the FZ and an overaging zone which is farther away from the FZ because of an alteration of the strengthening precipitates,resulting in different microhardness values,and the grains in the HAZ are elongated as same as the base metal (BM) and they do not become coarser compared with the BM.The minimum microhardness of the joint is obtained in the FZ and the value is approximately HV 1200 MPa,and that of the BM is about HV 1840 MPa,and the ultimate tensile strength of joints is 421.75 MPa which is 65.08％ of that of the BM.Samples of the tensile test fracture at the FZ and the fractured surface is of ductile fracture characteristics.Small particles whose composition is almost same as the compound T phase are observed at the bottom of dimples.
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