Abstract
Three thermal frequencies that were designated as 3, 4, and 5 Hz were used to reveal the microstructural evolution, mechanical, and corrosion properties of AA6061-T6 sheets that were welded by double pulsed gas metal arc welding (DP-GMAW) using microstructural observations, microhardness tests, tensile tests, bend tests, impact tests, and corrosion tests. A self-developed welding system consisted of a digital multifunctional welder and an arc dynamic waveform wavelet analyzer was chosen to perform welding operations and to record electrical signal waveforms during the welding process. The results show that the process of DP-GMAW was stable, and the weld beads exhibited aesthetic ripples. The ripple distance, the grain size, and porosity of the fusion zone decreased with an increasing thermal frequency. Microhardness and corrosion properties of the weld joint improved when the thermal frequency increased. In addition, all of the joints exhibited excellent bending properties. However, the impact property of the weld joint was lower than that of the BM. It indicated that the low impact energy results of the welded AA6061-T6 sheet were mainly due to the formation of micro-cracks in the fusion zone.
Highlights
Aluminum alloys have been extensively applied in automobiles, high-speed trains, naval vessels, and the aerospace industry due to the advantages of lightweight, excellent corrosion resistance, splendid impact resistance, and convenient to recycle [1,2,3]
The results showed that the joints of double pulsed gas metal arc welding (DP-GMAW) had superior microhardness and tensile properties
The results indicate the more Mg2 Si precipitate are distributed in the matrix when the thermal frequency is higher, thermal frequency significantly affects the precipitation of Mg2 Si
Summary
Aluminum alloys have been extensively applied in automobiles, high-speed trains, naval vessels, and the aerospace industry due to the advantages of lightweight, excellent corrosion resistance, splendid impact resistance, and convenient to recycle [1,2,3]. Along with the increasing demand of improving the processing quality of aluminum alloys, new welding methods continuously appear, such as double pulsed gas metal arc welding (DP-GMAW), cold arc welding, friction stir welding, cold metal transfer welding, and laser hybrid welding [4,5,6,7,8]. Among all of these methods, DP-GMAW has garnered increasing attentions due to its low cost, high productivity, and perfect welding quality [9]. The main characteristic of DP-GMAW is the coexistence of high frequency and thermal frequency [12]
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