焊接热输入和焊后热处理对搅拌摩擦焊2024-T3铝合金焊核区硬度的影响

摘要

在不同焊接热输入条件下对2024-T3铝合金进行搅拌摩擦焊接，并利用透射电镜、差热分析和维氏硬度测试对焊核区的组织和硬度进行分析检测。研究表明，焊核区的硬度受到焊接热输入的影响。在高焊接热输入条件下，焊接速度的提升有利于提升焊核区硬度。而在低焊接热输入条件下，焊核区硬度随着旋转速度的增加而增加。焊后热处理导致组织过时效，焊核区硬度降低。相比于其他参数下获得的焊核区，旋转速度为500 r/min，焊接速度为100 mm/min条件下获得的焊核区拥有较高的抗过时效性能，硬度下降仅为3.8%，而其他焊核区的硬度下降超过10%。焊核区硬度主要受到强化相形态的影响。%The microstructure and hardness of the stir zone (SZ) with different welding heat inputs were investigated for friction stir-welded 2024-T3 aluminum by transmission electron microscopy, differential scanning calorimeter and Vickers micro-hardness test. The results show that welding heat input has a significant effect on the hardness of the SZ. Under high welding heat input condition, a higher welding speed is beneficial for improving the hardness of the SZ. However, when the welding heat input is low, the hardness of the SZ elevates with increasing the rotation speed. The hardness of the SZ decreases after post-welded heat treatment due to overaging. The joints welded at 500 r/min and 100 mm/min show a high resistance to overaging. The reduction of hardness in the SZ is only 3.8%, while in other joints, the reduction is more than 10%. The morphology of strengthening precipitates plays important roles for the improvement of hardness.