Multiscale modeling of grain structure control in wire arc additive manufacturing of Ti6Al4V

To address the challenges of microstructural control and the correlation between process parameters and grain morphologies in wire arc additive manufacturing (WAAM), a three-dimensional multiscale model incorporating macroscopic finite element modeling (FEM) and microscopic phase-field modeling (PFM) was developed. The results indicate that temperature variations in space G and temperature variations in the time domain R are the main factors determining the relationship between the macroscopic process parameters and the microstructure in WAAM. An increase in the melt pool geometry leads to a decrease in G / R and an increase in G × R , which promotes the transformation from columnar to equiaxed grains and results in a decrease in the microscopic grain size. Increasing the scanning speed from 300 to 600 mm/min resulted in a 28.6% decrease in the equiaxed grain average area and a 15.97% decrease in the average columnar grain width. Extending the interlayer cooling time reduced the columnar grain average width by 11.7% and the equiaxed grain average area by 11.1%.