6005A-T6铝合金高速搅拌摩擦焊接头微观组织和力学性能

Microstructure and mechanical properties of 6005A-T6 aluminum alloy joint by high speed friction stir welding

采用专用搅拌摩擦焊设备对5 mm厚6005A-T6铝合金单层带筋板进行高速焊接,利用金相组织观察、显微硬度测定、拉伸、疲劳测试等方法研究高速搅拌摩擦焊接头的微观组织特征和力学性能。结果表明:焊核区由于发生了动态再结晶,其组织为细小等轴再结晶组织;焊缝两侧的热影响区受力和热的双重作用,组织发生一定程度的变形和回复;热影响区组织与母材相似,受热循环作用发生粗化。力学性能试验表明,在焊接速度3 000 mm/min、旋转速度1 700 r/min时,所得到的接头抗拉强度可达235 MPa,为母材的82.5%,拉伸试样均断裂于近缝区热影响区,与显微硬度分布测定的热影响区软化区位置相一致。疲劳试验表明,高速焊接接头疲劳性能优异,在循环次数1×106次的条件下,疲劳极限达132.9 MPa,能够满足工程要求。

In this paper,6005A-T5 aluminum alloy plate was friction stir welded using a high welding speed. The rnicrostructure evolution of different zones of the joint were investigated using various characterization methods. Mechanical properties of the joint were evaluated through tensile tests and micru-hardness measurements. It was shown that the nugget zone had fine equiaxed grains due to the dynamic recrystallization. The thermo-meehanically affected zone was characterized by plastic deformed and recovered structure because of the stains and thermal cycle subjected during the FSW prucess. The heat affected zone retained the same grain structure as the parent material,but grain coarsening occurred,whieh was also attributed to the thermal cycle during welding. The tensile strength of the joint reached 82.5% of the base material, and all the tensile specimens were fractured at heat affected zone, which was confirmed as softening region by microhardness measurement. In the condition of 106 cycles,fatigue limit at 132.9 MPa.The presented data of fatigue test provides solid base for pratical application.