An Analysis of the Mapping Relationship between Microstructure and Solidification Parameters during Aluminum Fused Coating

Metal fused-coating technology has the advantages of both low cost and high efficiency and is a new additive manufacturing technology in recent years. The previous studies were mainly aimed at the optimization of process parameters and the control of the surface quality of parts, while there were few theoretical analyses on the microstructure morphology after solidification. A three-dimensional transient numerical model was established to calculate temperature gradient and solidification rate, considering the changes in material physical properties with temperature during the calculation process. The temperature gradient on the substrate surface is jointly affected by the melt flowing out of the nozzle and the welding arc. It was found that the solidification front of the aluminum alloy was in an unstable state during the coating process. When the value of G/R decreases, the microstructure of the solidification interface gradually changes from columnar crystals to columnar dendrites and equiaxial crystals. The microstructure at the bottom of both the molten pool and coating layer is columnar crystal, while the microstructure at the upper part is equiaxed crystal.