A digital twin of synchronized circular laser array for powder bed fusion additive manufacturing

Abstract

The formation of undesirable microstructures and defects hinders the widespread use of additive manufacturing, e.g., the formation of columnar grains in Ti–6Al–4 V leads to undesirable anisotropic mechanical properties. Here, we investigate the application of a novel synchronized circular laser array in the powder bed fusion technique to alter the microstructure of printed parts toward the preferable equiaxed grains. This feat is not achievable with the single laser powder bed fusion technique for Ti–6Al–4 V alloy. The temporal temperature distributions for different process parameters (laser power, scanning speed, and internal distance between lasers in the array) were obtained by an anisotropic heat transfer model, and the Hunt criterion was employed to construct the solidification map. The results revealed that a degree of overlap between lasers is recommended to form a coherent melt pool, avoid degeneracy in surface quality, and maintain adequate resolution for all processing windows. However, laser overlap is not required for low scanning speed and high power scenarios. Finally, microstructure prediction shows that 45% of printed track includes equiaxed grains at a high power regime (500 W). However, the volume fraction of the equiaxed microstructure is reduced by decreasing laser power.