The influence of laser power on microstructure and properties of laser welding-brazing of Al alloys to Al-Si coated 22MnB5 steel

Abstract

Laser welding-brazing of 5052 aluminum alloys and Al-Si coated 22MnB5 steel was carried out with a Zn-22Al filler metal. The influence of laser power on weld appearance, interfacial microstructure and mechanical properties were investigated. The weld morphology and the interfacial microstructure changed significantly with laser power. When the laser power was 1500 W, the intermetallic compounds (IMCs) at the FZ/steel interface consisted of Fe2Al7Si which was pre-existed in the Al-Si coating. As the laser power increased from 1700 W to 2100 W, the interfacial IMCs changed to Fe2Al5-xZnx and FeZn10. With the increase of the laser power, the tensile strength raised first and then decreased, the maximum value of 135.0 N/mm was obtained at 1900 W laser power. Differently, the bending angle first decreased and then increased with the increase of laser power. Numerical simulations showed that the maximum interfacial temperature increased from 835.7 ℃ to 1424.6 ℃ as the laser power increased from 1500 W to 2100 W. It resulted in the total dissolution of Fe2Al7Si and the newly generation of Fe2Al5-xZnx and FeZn10 therefore inducing the change of joint mechanical properties.