Influence of spatial power modulation on pore and crack formation in laser beam welding of aluminum

The effect of spatial power modulation (SPM)—also known as wobble—for the welding of aluminum alloys has been investigated in laser beam microwelding. As the superposition of a high frequency circular oscillation movement and a global feed, two new parameters (A—amplitude and f—frequency) are added to the typical process parameters P—power and vw—welding feed rate. Microscopic and metallographic analyses have been used to determine crack appearance and position. With the choice of a sufficient ratio of A, f, and vw, the cooling behavior can be influenced. This also has an impact on the crack formation. Furthermore, the circular movement influences the local speed of the laser beam which in turn can affect the pore formation. The same effect appears on the depth stability as the keyhole formation strongly depends on the speed of the laser beam. The pore formation and weld depth stability have also been analyzed to determine the difference between conventional welding and welding with SPM.