Abstract
In this manuscript, weld pool dynamics in laser welding of various series of aluminum alloys were investigated by the in situ X-ray phase contrast imaging system. The experimental results showed that metal irradiated by laser was evaporated immediately, which generated the keyhole. Then metal surrounding the keyhole was melted gradually with the heat from keyhole. The growth rate of keyhole depth had a positive linear correlation with the total content of low boiling temperature elements (TCE), so did the keyhole depth and diameter at the stable stage. Longitudinal view area of the molten pool had a negative linear correlation with the thermal conductivity of aluminum alloy. The measured laser absorption rate had the same variation trend with the ratio of keyhole depth to diameter, and the highest absorption rate of 58% appeared in laser welding of aluminum alloy with TCE equal to 2.1%. Violent fluctuation in keyhole shape was avoided in aluminum alloy with TCE lower than 2.1%, where the surface tension and recoil pressure of metal vapor were balanced. To sum up, the effect of alloy element on weld pool dynamics in laser welding of aluminum alloys was firstly quantified in this manuscript.
Highlights
Aluminum alloy is one of key materials in weight saving of mobile body including electric vehicle (EV)
Several researchers found that Mg element in aluminum alloy evaporated during the laser welding process, which would affect the characteristics of keyhole dynamics, and the final properties of the weld bead, e.g. hardness distribution, welding defect including undercut and porosity[31,32,33,34,35]
Keyhole and molten pool were captured by X-ray phase contrast imaging system to reveal the quantitative relationship between the observed characteristics and composition of aluminum alloys
Summary
Aluminum alloy is one of key materials in weight saving of mobile body including electric vehicle (EV). By placing a camera at the glass side, it is possible to directly capture the inside behavior of the weld pool, which contributed a better understanding of the keyhole dynamics and flow of the molten pool This specially designed structure changed the heat conduction condition around the weld pool, and the measured keyhole size was clearly larger than the real one in laser processing. The relationship between aluminum alloy with different compositions and behavior of weld pool induced by laser is still not fully understood In this manuscript, X-ray phase contrast imaging system was adopted to capture the weld pool behavior and porosity formation process in laser welding of various series of aluminum alloys. This paper provided a quantitative research about effect of alloy element on weldability of aluminum
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