Effects of diode laser superposition on pulsed laser welding of aluminum

Abstract

Pulsed laser welding of thin aluminum sheets is common for housing, where welding defects are detrimental especially in terms of hermetic packaging as well as electromagnetic compatibility. This paper shows investigations on laser welding of aluminum by superposition of a pulsed Nd:YAG laser with a diode laser in order to improve the weldability of aluminum. This configuration allows to enhance the absorption of the Nd:YAG welding laser due to preheating by the diode laser. Furthermore the effects of temporal pulse shaping have been studied experimentally. Deeper penetrations as well as an increased weld quality in terms of cracking were observed in welds manufactured with diode laser superposition. Besides this the modification of the thermal cycle by the combination of the two laser beams promotes advantageous solidification conditions and therefore hot cracks were efficiently reduced or avoided. Additionally solidification conditions can be actively influenced. The results show a decreasing number of defects and additionally an increase of the welding quality.