Effect of ultrasonic vibration field on tungsten inert gas welding of magnesium alloy and galvanized steel

Abstract

In this paper, the authors introduced ultrasonic vibration into the molten bath via ultrasonically vibrating welding wire and investigated the effect of ultrasonic vibration on the mechanical properties, microstructures and macrostructures of tungsten inert gas (TIG) welded AZ40 Mg alloy and DP780 galvanized steel joints. The main results are summarized as follows. During the ultrasonic vibration aided TIG welding, ultrasonic vibration can improve the wettability of welding pool on the steel plate and eventually increase the width of welding seam than that without ultrasonic vibration. The average grain size of fusion welding area is obviously reduced with the assistance of ultrasonic vibration and gives rise to the increase of micro hardness. A 4 μm thickness intermetallic compound layer occurs at the brazing area of joint and the ultrasonic vibration aided process has no obviously effect on the microstructure of brazing area of Mg/steel joint. The maximum tensile strength of Mg/steel workpiece increases 8.2% to 252 MPa over the workpiece welded without ultrasonic vibration, owing to the effective refinement strengthening. Besides, the fracture surface of Mg/steel workpiece obtained with the aid of ultrasonic vibration is characterized with more plastic fracture features.