Columnar-to-Equiaxed Transition on Laser Powder Bed Fusion Ultra-Precision Additive Manufacturing Accuracy and Surface Roughness for Solidified 316L Micro-Lattice Structure

The improvement of PBF manufacturing accuracy has been an urgent problem to solve. The columnar-to-equiaxed transition of rapid solidification during laser powder bed fusion (L-PBF) has been reported, while its influence on the accuracy and surface roughness of fabricated 316L micro-lattice structures remains to be studied. This study presents a novel fully coupled finite volume method for cellular automata (CA), integrated with response surface methodology (RSM), which is applied to investigate the columnar-to-equiaxed transition influence on the accuracy and surface roughness of ultra-precision additive manufactured 316L lattice structure by L-PBF. It is proven that the higher overlap is identified as the optimal strategy for improving both surface quality and dimensional accuracy. Both the CA model prediction and the experimental results reveal that the effect of latent heat releases from the grain refinement on the adhesion of the surrounding powder is an increment of the surface roughness, while the decrement of the surface quality and accuracy. The overlap strategy is promoted to be the most suitable measure to achieve both high surface quality and manufacturing accuracy. The surface roughness Ra (SP) can rapidly decrease by 68.6%, and the mean diameters decrease by 18.7% under the overlap strategy.