(1. 航天材料及工艺研究所，北京 100076;
2. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用圆柱形搅拌头和带螺纹搅拌头，制备2195-T8铝锂合金摩擦搅拌焊接头，研究搅拌头前进速度与旋转速度对接头孔洞缺陷的影响，分析接头的显微组织特征。结果表明:当圆柱形搅拌头旋转速度与前进速度比值不当时，在接头前进侧下部容易产生贯穿整个接头的隧道型缺陷(连续孔洞);采用带螺纹搅拌头可以消除接头的这种缺陷，有效提高接头抗拉强度。2195-T8铝锂合金基材中强化相包括T1相(Al2CuLi)和θ′相(Al2Cu);热机影响区所有θ′相及大部分T1相溶解;而焊核区T1相和θ′相均完全溶解，并在焊核区产生较多位错。热影响区和基材为沿轧制方向的板条状晶粒;热机影响区晶粒发生偏转和变形;焊核区晶粒均发生再结晶，但焊核区边缘近热机影响区再结晶晶粒尺寸较小，而中心焊核区再结晶晶粒长大。
关键字: 2195铝锂合金;摩擦搅拌焊;孔洞缺陷;接头组织
（1. Aerospace Research Institute of Materials and Processing Technology, Beijing 100076, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The friction stir welding (FSW) joints of 2195-T8 Al-Li alloy were prepared by straight cylindrical pin and threaded cylindrical pin. The effect of rotational speed and welding speed on the hole defect was investigated, and the microstructure of the FSW joint was observed. The results show that when the straight cylindrical pin is used at an inappropriate ratio of rotational speed to welding speed, continuous hole (or tunnel) at the bottom of advancing side forms. Meanwhile, this defect can be eliminated by the threaded cylindrical pin, and the joint strength is effectively enhanced. The strengthening precipitates of 2195-T8 Al-Li alloy consist of T1 (Al2CuLi) and θ′(Al2Cu). In thermo-mechanically affected zone (TMAZ), all θ′ precipitates but most T1 precipitates are dissolved. While, all the θ′ and T1 precipitates in nugget zone (NZ) are dissolved, and a lot of dislocations generate. The TMAZ grains under go deflection and deformation during the welding process. The NZ grains are recrystallized, and the recrystallized grains of the NZ close to the TMAZ are larger than those of the NZ center.
Key words: 2195 Al-Li alloy; friction stir weld; hole defect; joint structure
