Abstract
A novel ultrasonic vibration-assisted welding (UVAW) process was used to achieve reliable joining of galvanized steel and Mg alloy. The effects of the UVAW technique on the microstructure and mechanical properties of galvanized steel/Mg alloy weldment were studied in detail. The introduction of ultrasonic vibration can ameliorate the wetting of welds and eliminate porosity defects. A refined microstructure of the fusion welding zone with an average grain size of 39 ± 1.7 µm was obtained and attributed to cavitation and acoustic streaming caused by the UVAW process. The grain refinement led to an increase in the microhardness and joining strength of the galvanized steel/Mg alloy weldment. Under the ultrasonic power of 0.9 kW and a current of 65 A, the maximum joining strength of the ultrasound-treated galvanized steel/Mg alloy joint was 251 ± 4.1 MPa, which was a 14.6% increase over the joint without ultrasonic treatment.
Highlights
With increasing demand from consumers and the environment for high fuel efficiency vehicles, as well as for the reduction of carbon dioxide emissions from vehicles, nonferrous metals, as a good substitute for traditional metal alloys, have attracted much attention [1,2,3].nonferrous alloys based on aluminum (Al) [4], magnesium (Mg) [5,6], and titanium (Ti) [7] with high specific strength, superior processability, and easy recycling have been developed and used in automobile manufacturing and aerospace fields
It is confirmed that the sound galvanized steel/AZ31B joint was obtained by the ultrasonic vibration-assisted welding process
Ultrasound-induced acoustic streaming and cavitation significantly refined the microstructure of the weld zone, and its average grain size was about 39 ± 1.7 μm
Summary
With increasing demand from consumers and the environment for high fuel efficiency vehicles, as well as for the reduction of carbon dioxide emissions from vehicles, nonferrous metals, as a good substitute for traditional metal alloys, have attracted much attention [1,2,3]. Xu et al [12] studied the effects of an aluminized zinc coating on the tensile strength and microscopic interface characteristics of steel/Mg weldment. According to Wang, ultrasonic vibration can affect the size and morphology of austenite grains during the solidification of the weld pool and promote the formation of a large number of fine ferrite structures in the subsequent solid phase transformation of the weld metal. Ultrasonic vibration made the columnar structure of the welded metal more refined, achieving a good balance of high tensile strength and impact toughness. The present study attempted to introduce ultrasonic vibration into the liquid metal of molten pool through filler wire, aiming to improve the microstructure and performance while minimizing the adverse effects of vibration on the entire weldment. The evolution of joint appearances, the weld microstructure, and mechanical performances were systematically investigated
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