On the occurrence of weld bead porosity during laser vacuum welding of high pressure aluminium die castings

Abstract

Due to porosity and incomplete fusion, aluminium high pressure die castings are materials that are known to be difficult to weld. Hereby porosity is mainly caused by hydrogen which is trapped within the weld bead during solidification as a result of insufficient degassing. To enhance degassing and to reduce the influence of surrounding air, laser vacuum welding was applied within the current study. The main goal was to investigate the occurrence of porosity during laser beam welding of aluminium high pressure die castings. To reach this aim, die casting plates were laser welded at varied ambient pressure and investigated by x-ray computed tomography. The analysis of the welds focuses on the size, position, amount and shape of the detected defects depending on the ambient pressure during welding. The results showed a dependency of the occurrence of porosity and the ambient pressure whilst welding.