水冷辅助铝/镁异材搅拌摩擦焊接头 金属间化合物析出行为

文章在大气与水冷辅助下分别对 2 mm 厚的 AZ31B/6061-T6 异种合金薄板进行搅拌摩擦对接焊接，并分析水冷对搅拌摩擦焊（friction stir welding，FSW）异质接头脆性金属间化合物（intermetallic compounds，IMCs）析出行为的影响。结果表明：水冷接头焊接时的峰值温度和高温停留时间均低于大气焊接时，焊缝平均焊接温度低于 $ 350\;^{\circ}C $，且温降速率更快；水冷辅助 FSW 接头脆性 IMCs 的析出量较大，辅助 FSW 有所减少，界面处 IMCs 层厚度显著降低；水的比热容较大，能够有效吸收焊接热，冷却效果显著，但也导致材料塑性流动遭到削弱，易引起接头隧道缺陷的发生以及诱发淬火残余应力。

AZ31B/6061-T6 dissimilar alloys sheets with thickness of 2 mm were used to carry out friction stir butt welding, which were under atmosphere and water-cooled assisted conditions, respectively. The influence of water-cooled condition on the precipitation behavior of brittle intermetallic compounds (IMCs) in dissimilar friction stir welding (FSW) joints was studied. Results show that peak temperature and high temperature duration of joints under water-cooled condition were lower than those under atmospheric condition, which exhibited an average welding temperature of 350 °C at welding line and a faster cooling rate. Besides, the precipitation of brittle IMCs in water-cooled assisted FSW joints was decreased comparing to that under atmospheric condition, and the thickness of IMCs was apparently decreased. Specific heat capacity of water is high, which can effectively absorb welding heat and has a remarkable cooling effect. However, it also weakens the plastic flow of materials, which may lead to tunnel defects and induce quenching residual stress.