Effect of laser pulse on recovery delay of arc plasma based on ion migration behavior in the pulsed laser–arc hybrid welding process

This paper presents the investigation on effect of laser pulse on the recovery delay of arc plasma during pulsed laser–arc hybrid welding of Mg alloy based on the dynamic behavior of Mg atoms. High-speed camera and spectrograph are employed to monitor the behaviors of Mg atom in the arc plasma and to characterize the effect of laser pulse on the arc plasma, respectively. It is found that the arc plasma cannot recover to its original state immediately after laser pulse action and it takes 0–5 ms for the excessive Mg atoms to escape from the arc plasma depending on the given parameters. According to the calculation, time for Mg ions to travel from the anode to the cathode in the conduction channel of the arc plasma is less than 0.1 ms. The high temperature of the laser keyhole region on the base material surface still exists when the laser pulse is removed and sustaining supply of the Mg ions from this region is the essential factor influencing recovery delay of the arc plasma.

► There is a recovery relaxation of arc plasma state after laser pulse action.
► It takes about 0.083 ms for the Mg ions to travel from the plasma anode to cathode.
► Sustaining supply of Mg ions from material responds to the recovery relaxation.
► Region on material with high temperature still exists after a laser pulse action.