1561铝合金搅拌摩擦焊接头微观组织分析

采用恒压力控制模式对4 mm厚1561铝合金板材进行了搅拌摩擦焊接试验，并对接头微观组织进行了研究. 结果表明，随着由母材向焊缝中心过渡，晶粒尺寸呈先增大后减小的趋势，小角度晶界占比和位错密度持续降低. 其中，热影响区晶粒在焊接热循环的作用下发生长大. 热力影响区由被拉长的条状晶粒及细小等轴晶组成，表明此区域发生部分动态再结晶. 搅拌区晶粒呈细小的等轴晶形态，说明该区域发生了完全动态再结晶. 与母材区数量较小且尺寸较大的沉淀相相比，搅拌区存在大量尺寸较小的Al₆Mn相，说明此区域沉淀相发生了先溶解再析出的过程. 同时，搅拌区存在明显的位错墙和亚晶界等亚结构，表现出连续动态再结晶的组织形成特征. 搅拌区内Al₆Mn相主要分布在位错上，起到了钉扎位错并阻碍再结晶晶粒长大的作用.

Study on microstructures of friction stir welded joint of 1561 aluminum alloy

4 mm thick 1561 aluminum alloy was friction stir welded by the constant pressure controlling mode, and the microstructures of the FSW joint were studied. The results showed that the grain size first increased and then gradually decreased from the base material to the weld center, and the low-angle boundary proportion and the dislocation density continued to decrease. In HAZ, the grains grew under the action of the welding thermal cycle. The grains in TMAZ were composed of elongated grains and fine equiaxed crystals, and partial dynamic recrystallization occurred in this zone. The grains in SZ were fine equiaxed, indicating that complete dynamic recrystallization occurred. Compared with the precipitates with smaller number and larger size in the base metal zone, there were a large number of Al₆Mn phases with smaller size in the SZ, indicating that the precipitates in this zone dissolved first and then precipitated. At the same time, there were obvious substructures such as dislocation walls and subgrain boundaries in the SZ. This indicated that continuous dynamic recrystallization occurred. The Al₆Mn phase mainly distributed on the dislocations in the SZ, and this could pin the dislocations and hinder the growth of recrystallized grains.