Abstract
Aluminum alloy has been widely used due to its excellent workability, and double-pulse metal inert gas welding (MIG) has become a popular technique in aluminum alloy welding. In this study, a cross-complementary test was performed to study the effect of double-pulse characteristics on weld bead formation and mechanical properties in MIG welding. The test was carried out on an AA6061 aluminum alloy using flat overlaying welding. After welding, the micro-metallographic structure and macro-mechanical performance of the weld bead were explored. The test results showed that the two methods of increasing the base current amplitude or the low-frequency of the current effectively enhanced the oscillation of the molten pool, refined the grain size of the fusion zone, and improved the mechanical properties of the weld. Additionally, by comparing the macroscopic photograph of the specimen and the corresponding welding parameters in the test, the formation characteristics of the bead’s fish-scale pattern in double-pulse MIG welding were found when appropriate welding parameters were adopted and weld bead formation was good. This test result provides a strong scientific basis for the selection of welding parameters in the actual promotion and application of double-pulse MIG welding.
Highlights
As a type of light alloy whose annual global output is second only to steel, aluminum alloys have quickly attracted attention in the fields of aerospace, automobiles, ships, bridges, machinery manufacturing, and others, and has been widely used since it emerged in the aviation industry due to its excellent workability, corrosion resistance, impact resistance, and other properties [1,2]
Mathivanan et al showed that the periodic alternation between strong and weak groups of double pulses could enhance the oscillation of the molten pool and refine the crystal grains [5,6]
The base metal used was an AA6061 aluminum alloy that is widely used in many important industrial fields such as aviation, aerospace, subway vehicles, railway passenger cars, etc. [15,18]
Summary
As a type of light alloy whose annual global output is second only to steel, aluminum alloys have quickly attracted attention in the fields of aerospace, automobiles, ships, bridges, machinery manufacturing, and others, and has been widely used since it emerged in the aviation industry due to its excellent workability, corrosion resistance, impact resistance, and other properties [1,2]. The low melting point, high thermal conductivity, and large linear expansion coefficient of aluminum alloys can result in defects such as deformation, pores, and thermal cracking during welding [3,4]. The melting point of the protective oxide film on the surface of the aluminum alloy is high and makes it challenging to generate a welding arc. Double-pulse MIG welding has become a popular research topic in aluminum alloy welding due to its simple process, wide current adjustment range, low porosity, and small grains in the fusion zone. Mathivanan et al showed that the periodic alternation between strong and weak groups of double pulses could enhance the oscillation of the molten pool and refine the crystal grains [5,6]. Jin Li found that changing the difference between the base current of the strong and weak pulse groups was the ideal mode for double-pulse
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