Multiscale modelling of microstructure, micro-segregation, and local mechanical properties of Al-Cu alloys in wire and arc additive manufacturing

Wire and Arc Additive Manufacturing (WAAM) is a combination of welding and AM technologies and uses an electric arc as the heat source to melt welding wire. The mechanical properties of WAAM components are greatly dependent on the solidification behavior and microstructure. In this paper, a model composed of a macroscopic finite element (FE) model combined with a microscopic phase field (PF) model was constructed to investigate the Al alloy microstructure evolution during WAAM. First, the FE model was implemented to calculate the temperature gradient and solidification speed under different processing parameters. These results were then fed into the PF model to simulate the microstructure and concentration field of chemical compositions. The simulated results indicate that the moving speed of the substrate has a pronounced impact on the primary dendrite arm spacing (PDAS), which grew significantly as the moving speed increased, while the PDAS decreased slightly upon increasing the electric current. Furthermore, the solute distribution analysis showed that micro-segregation formed during the solidification process, and that current and substrate speed had evident impact on the micro-segregation ratio. Finally, metallographic experiments, energy-dispersive spectrometer analysis for element distribution, and miniature tensile tests were conducted on the specimens to validate the PF simulated results and obtain the relationship between process parameters and mechanical properties.