Optimization of selective laser melting (SLM) fabrication quality for Ti6Al4V alloy: experimental and numerical study with introduction of remelting process

This study aims to improve the quality of titanium alloy structural components by introducing a remelting process into conventional selective laser melting (SLM) fabrication. To address common defects such as porosity, roughness, and stress deformation, a twofold study was conducted by developing a three-dimensional finite element model together with experimental verification. First, through a series of experiments and numerical simulation, the influence patterns of the remelting process parameters on the melt pool behavior and surface quality were investigated. The results show that excessive remelting power and insufficient remelting speed lead to an unstable melt pool, resulting in the formation of keyholes inside the melt pool and increased porosity in the formed parts. On the other hand, insufficient remelting power and excessive remelting speed can result in short exposure time of the molten pool and limited laser penetration capability, leading to incomplete melting of powder particles, thus increasing the surface roughness of the formed part. Furthermore, through experimental investigation and simulation analyses, the influence patterns of remelting strategies on the temperature field and stress distribution of the melt pool were investigated. The investigation reveals that the introduction of remelting strategies can reduce the temperature gradient of the melt pool. Because of the variation of thermal conductivity in the surrounding area, the temperature gradient at the edges was higher than that at the center for all strategies. Different laser scanning directions also resulted in varying magnitudes of residual stress in the X- and Y-directions under each strategy. In the spiral remelting path, high thermal stresses were observed at the center, resulting in higher residual stresses than those at the edges. These findings provide essential guidance for optimizing the SLM fabrication process and enhancing the quality of formed components.