AA6061-T6与AZ31合金异种搅拌摩擦焊接头的微观组织

研究了AA6061-T6和AZ31合金异种搅拌摩擦焊接头的微观组织。在异种搅拌摩擦焊接AA6061-T6与AZ31合金时，采用偏置条件，即将搅拌针插入时偏向AZ31合金，从而得到异种对接接头。通过预备实验来优化搅拌针的前进速度、旋转速度。运用电子背散射衍射技术观察搅拌区的纹理，并得到粒径分布和错位角分布，在搅拌区存在相对精细的晶粒结构。在AA6061-T6搅拌区出现随机或弱面取向，而在AZ31搅拌区出现旋转底面取向。再结晶颗粒的平均尺寸只有2．5～4．5μm。与基础合金相比，在AA6061-T6搅拌区的大角度晶界的分数增大，而在AZ31搅拌区的小角度晶界的分数降低。

Microstructure of stir zone in dissimilar friction stir welds of AA6061-T6 and AZ31 alloy sheets

This study was performed to investigate microstructure of dissimilar friction stir welds manufactured with AA6061-T6 and AZ31 alloy sheets. Dissimilar butt joints were fabricated under the ＇off-set＇ condition that tool plunge position shifted toward AZ31 from the interface between AA6061-T6 and AZ31. Optimized tool rotating speed and its traveling speed were selected through a lot of preliminary experiments. Electron back-scatter diffraction （EBSD） technique was applied to measure texture in the stir zone （SZ）. Grain size distribution and misorientation angle distribution were also obtained. A remarkably fine-grained microstructure was observed in the SZ. Randomized or weaker plane orientations were formed in the SZ of AA6061-T6, while rotated basal plane orientations were concentrated in the SZ of AZ31. Average size of recrystallized grains was measured as just 2.5—4.5 μm. The fraction of high-angle boundary in the SZ of AA6061-T6 increased and that of low-angle boundary in the SZ of AZ31 decreased compared with the base metals.