静轴肩辅助铝镁搅拌摩擦搭接接头的组织与性能

Microstructure and mechanical properties of Mg/Al friction stir lap welding joint assisted by stationary shoulder

文中将静止轴肩技术应用到铝镁异种合金的搅拌摩擦搭接过程中,并分析了焊接速度对接头成形和力学性能的影响.结果表明,静止轴肩能够增强上下板之间的材料交换,焊后搅拌区呈较大的洋葱环形貌,其内部分布大量的金属间化合物;搭接面处发生良好的冶金结合.由于生成金属间化合物,洋葱环区域的显微硬度值明显高于接头其它区域.X射线衍射结果表明,金属间化合物的主要成分是Al_3Mg_2和Al_(12)Mg_(17).接头的抗拉强度随着焊接速度的增加呈先上升后下降的趋势,最大值在焊接速度为40 mm/min时取得.

In this work,stationary shoulder was used in friction stir lap welding(FSLW)of dissimilar magnesium alloy to aluminum alloy.Effect of the welding speed on microstructure and mechanical properties of the lap joint were mainly studied.Results show that the stationary shoulder can enhance the material mixing between the two alloys.The stir zone(SZ)is characterized by a big onion ring after welding,in which plenty of intermetallic compounds(IMC)can be obtained.Excellent metallurgical bonding can be observed at the lap interface.Microhardness of the onion ring is higher than other regions of the joint due to the IMC.X-ray diffraction(XRD)pattern analysis shows that the main IMCs formed in the SZ are Al_3Mg_2and Al_(12)Mg_(17).Lap shear failure load of the joint firstly increases and then decreases with increasing the welding speed.The maximum load is obtained when using 40 mm/min.