Process investigation on ultrasonic vibration enhanced friction stir welding of 2195 aluminum-lithium alloy

Abstract

A novel ultrasonic vibration enhanced friction stir welding (UVeFSW) process was employed to join the rolled 2195 aluminium-lithium alloy of 4 mm thickness. The effects of superimposing ultrasonic on the macro metallograph,microhardness and tensile properties of welded joints were compared and analyzed. The effect of process parameters on the weld formation and joint mechanical properties of aluminium-lithium alloy by ultrasonic vibration enhanced friction stir welding was investigated. The results show that under the same process parameters superimposing ultrasonic energy in friction stir welding can improve the formability of 2195 aluminium-lithium alloy and enhance the plastic material flow in the weld nugget zone, which can reduce or even eliminate the void defect in the conventional friction stir welding joint. The microhardness at the top and middle of the nugget zone increases due to the ultrasonic effect, while the bottom of the weld does not change much. The fracture surfaces of the joints show a ductile fracture mode, and the elongation of the joints increases after ultrasonic vibration energy is applied, and the fracture dimples are more fine and uniform. Under the welding parameters studied the maximum tensile strength and elongation of the joint are 282.8 MPa and 11.5%, respectively. Under the conditions with rotational speed of 600 r/min and welding rate of 225 mm/min, the application of ultrasound can improve the tensile strength and the elongation of the joint by 17.5 MPa and 3.7% respectively.

Keywords

• aluminium-lithium alloy
• friction stir welding
• ultrasonic vibration
• mechanical property