Pulsed laser welding with Nd:YAG lasers is applied for welding of thin aluminum sheets when the heat affected zone has to be minimized. Due to the pulsed operation of the Nd:YAG laser and the low absorptivity of aluminum for infrared radiation ({\~}5 \% @ 1064 nm) the achieved welding speed is small in comparison to continuous laser welding processes. In this study, a conventional pulsed Nd:YAG laser is superposed with a diode laser (output power up to 100 W) to weld AlMg1 sheets with a thickness of 1.5 mm. The diode laser operates at a wavelength of approximately 808 nm in order to meet the absorption maximum of aluminum at this wavelength ({\~}15 \% @ 808 nm). The diode laser is emitting laser pulses with a pulse length of up to 200 ms which are synchronized with the laser pulses of the Nd:YAG laser. With this combination an increase in penetration depth has been achieved due to preheating of the diode laser.