厚板铝合金搅拌摩擦焊接头的冲击性能

Impact Performance of Friction Stir Welded Joints of Thick Plate Aluminum Alloy

采用搅拌摩擦焊对厚度为30mm的2A12铝合金板材进行对焊连接,分析了接头不同厚度处的微观组织与冲击性能。结果表明:随着热输入量的减少,接头上层的晶粒相比于下层出现了粗化现象,导致接头上层区域的冲击韧性低于下层。焊核区晶粒最为细小,热机影响区次之,热影响区晶粒最为粗大;焊核区的冲击韧性高于热影响区,热机影响区由于存在微型裂纹,所以冲击韧性最低。焊核区上层的晶粒尺寸小于热机影响区下层的晶粒尺寸,但焊核区上层的冲击韧性低于热机影响区下层的冲击韧性,这是由于焊核区所含的Al_2CuMg脆性第二相的数量较多。焊接接头冲击韧性的变化不仅与焊缝不同区域的微观组织变化有关,还与该区域的第二相数量有关。

Butt welding of 2A12 aluminum alloy with thickness of 30 mm was conducted by friction stir welding, the microstructure and impact performance of the joints were analyzed at different thickness positions. The results showed that with the decrease of the heat input, the grain size in the upper part of the weld nugget zone （NZ） was coarsening compared to the lower part of NZ. Causing the impact toughness in the upper area of the joint lower than that in the bottom. The grain size was the smallest in the NZ, a little bit coarser in the thermo-mechanically affected zone （TMAZ）, and the coarsest in the heat affected zone （HAZ）. There existed difference in impact toughness of the welded joint. The impact toughness of NZ was higher than that of HAZ, The impact toughness of TMAZ was the lowest due to the existence of micro cracks. The grain size of the upper part of NZ was smaller than that of the bottom part of TMAZ, but the impact toughness of these two parts was just the opposite, because the number of the second phase （Al 2CuMg） was larger in NZ. In conclusion the change of impact toughness of welded joints was not only related to the microstructure variation, but also the amount of the second phase in the region.