Modelling and experimental observation of the deposition geometry and microstructure evolution of aluminum alloy fabricated by wire-arc additive manufacturing

Abstract

In this paper, a model composed of a macroscopic finite element (FE) model coupled with a microscopic phase field (PF) model was constructed to investigate the Al alloy microstructure evolution during wire arc additive manufacturing (WAAM). First, the relationships between single layer process parameters and the resulting deposition geometries (width and height) were investigated. A three-dimensional FE model was built to calculate the thermal distribution and temperature gradient under different process parameters. These results were then fed into a PF model to obtain the microstructure corresponding to each set of process parameters. A bridge was constructed by this method, starting from the WAAM process parameters and yielding the microstructure throughout solidification. The simulated results showed that the primary dendrite arm spacing (PDAS) decreased slightly with current increases, but the substrate moving speed had a more obvious impact on PDAS, which rose significantly with increased substrate speed. Finally, metallographic examination and energy dispersive spectroscopy tests were conducted on specimens fabricated by WAAM with different process parameters, to verify the simulated PF results. The simulated morphology and size of dendrites were in good agreement with experimental results.