Dimensionless relationships for the keyhole weld characteristics in AZ80 magnesium alloy

The keyhole welding of an AZ80 magnesium alloy has been investigated using a continuous 6-kW CO2 laser and measurements of both dimensions and chemical compositions of the fusion zone. All the experimental data were satisfactorily modeled using dimensionless numbers (suggested from the conduction theory of moving Gaussian heat sources) and empirical formulas (derived from least-square root analyses). Chemical compositions (measured by glow discharge spectroscopy) showed that the central region of the fusion zone was enriched in aluminum, but depleted in zinc, as could be expected by comparing the boiling temperatures of aluminum, zinc and magnesium. Although thermal cycles with focused laser beams also affected chemical composition, compositional changes were negligible, even with the most intense laser beams.