2195铝锂合金摩擦搅拌焊接头组织

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。%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 pinis used at an inappropriate ratio of rotational speedtowelding speed, continuous hole(or tunnel)atthe bottom of advancing side forms. Meanwhile, this defect canbe eliminated by the threaded cylindrical pin, and the joint strengthiseffectively enhanced. The strengthening precipitates of 2195-T8 Al-Li alloy consist ofT1 (Al2CuLi) andθ′(Al2Cu). In thermo-mechanically affected zone (TMAZ), allθ′ precipitates but mostT1 precipitatesaredissolved. While, all theθ′andT1 precipitates in nugget zone (NZ)aredissolved, and a lot of dislocations generate. The TMAZ grains undergo deflection and deformation during the welding process. The NZ grainsarerecrystallized, and the recrystallized grains of the NZ close to the TMAZarelarger than thoseof the NZ center.