Numerical investigations of arc plasma characteristic parameters evolution and metal properties in GMAW-based WAAM of Al alloy with an integrated model

Understanding the arc plasma characteristic parameters evolution and the metal thermodynamics is of great significance for guiding the improvement of the forming accuracy and performance of GMAW-based WAAM in engineering. In this study, we have developed a three-dimensional arc plasma-droplet-molten pool integrated model of GMAW-based WAAM of Al alloy, which simultaneously includes the heating of arc plasma, the vaporization of Al metal, the transfer of droplet, the melting and solidification of molten pool, and the relative motion between wire and substrate. Based on this sophisticated model, the effect of Al vapor on the arc plasma characteristics, the dynamic evolution of arc plasma characteristics during the metal transfer process, and the heat transfer and flow behaviors of liquid metal are comprehensively investigated. The simulation results show that the Al vapor is principally generated from the surface of droplet, which leads to the decrease of arc plasma temperature and arc pressure, and the expansion of current path. In a droplet transfer cycle, the average tem-perature of plasma decreases first and then increases, affected by the distribution of current density. Most of heat for the formation of molten pool comes from the energy transfer of droplet, and the droplet impact effect on the molten pool flow is significantly greater than Marangoni effect. Finally, the simulation results, including droplet transfer process and deposited layer profile, are validated by experimentally measured results, which are in good agreement with each other.