2198-T3S铝锂合金组合工艺搅拌摩擦焊接头组织性能分析

Analyses of Combination Process on Microsturctures and Properties of Friction Stir Welded Joints for 2198-T3S Aluminum-Lithium Alloy

为探究搅拌摩擦焊(FSW)焊接铝锂合金板材的最佳工艺参数,采用圆柱形螺纹搅拌头,焊前对板材背面开槽,在保持焊接速度不变的情况下对2198-T3S铝锂合金板材进行不同转速下的焊接组合工艺实验,焊后对接头进行了微观组织分析与力学性能测试。研究结果表明:采用组合工艺后焊缝的根部未出现弱连接缺陷;随着转速的提高,焊缝内部的缺陷消失,焊核区的晶粒呈粗大化趋势,第二相回溶,使焊缝的力学性能呈现“先升后降”的趋势。在最优组合参数下接头的抗拉强度和屈服强度分别为359 MPa(母材的81.5%)和248 MPa(母材的77.5%)。同时,转速的提高使焊缝的断裂方式发生了改变,由脆性-韧性混合断裂向韧性断裂转变。

In order to explore the optimum parameters of FSW for Al-Li alloy sheets,the combination processes were carried out in the welding processes.A cylindrical threaded tool was used during welding processes,the back of the sheets was slotted before welding and the experiments of 2198-T3S Al-Li alloy sheets were carried out at different rotational speeds under the conditions of maintaining the unchanged welding speed.The microstructures and mechanics properties of the joints were analyzed after welding.The results show that there is no weak connection defects at the root of the welds.With the increasing of rotational speeds,the defects inside the welds disappear,the grains in the nugget zones become coarser and the second phase particles dissolve,which lead to the trends of“first rising and then falling”in the mechanics properties of the welds.Under the optimum combination parameters,the tensile strength and yield strength of the joints are as 359 MPa(81.5%of base material)and 248 MPa(77.5%of base material)respectively.Meanwhile,with the increasing of rotational speeds,the fracture mode of welds is changed from brittle-ductile mixed fracture to ductile fracture.