AZ61A镁合金搅拌摩擦焊接头组织与性能研究

Study on microstructures and properties of friction stir welded joint of AZ61A magnesium alloy

通过拉伸、弯曲、金相、硬度以及脉动拉伸对采用搅拌摩擦焊焊接工艺的型号为AZ61A的4 mm镁合金进行焊接性能研究。试验结果表明:4 mm拉伸试件的断裂位置均位于热影响区,抗拉强度满足标准要求;所有的面弯和背弯试件均未出现断裂,弯曲性能较好;搅拌摩擦焊接头热影响区部分晶粒有所长大,焊核区为细小的等轴晶,组织由α(Mg)相和沿晶界分布的β(Mg17Al12)相组成,热机影响区晶粒大小不均匀,可观察到较明显的塑性流变带结构;焊核区的硬度分布近似为均值,且与母材的相差不大,热影响区的硬度最低;从脉动疲劳试验结果可以判定断裂位置在热影响区,为韧性断裂和准解理断裂的组合。

Tensile,bending,microstructure,hardness and pulsation tensile fatigue tests were carried out to study the microstructures and properties of 4 mm AZ61 A magnesium alloy friction stir welded joint.The results showed that the fracture locations of 4 mm tensile specimens were all located in the heat-affected zone,and the tensile strength met the standard requirements.All the bending specimens showed no breakage in bending and back bending and good bending performance.Some grains in the affected zone of the friction stir welding grew up while isometric crystal was found in the weld nugget.The microstructure consisted ofα(Mg)phase andβ(Mg17 Al12)phase distributed along the grain boundary.The grain size in the heat affected zone was not uniform and existed the obvious plasticity of the rheological band structure.The hardness distribution of the weld nugget area was approximately the average value and little difference with the base metal,and the hardness of the heat affected zone was the lowest.From the macroscopic appearance fatigue specimen of the pulsating tensile fatigue specimen,it could be seen that the fracture location located in the heat affected zone,the fracture was a combination of ductile and quasi-cleavage fractures.