Simulation Study on the Impact of Melt Track Overlap Rate on the Forming Result During the Selective Laser Melting of Ti-6Al-4V Alloy

The melt track overlap rate is a crucial process parameter in selective laser melting (SLM). It exerts a substantial influence on the forming quality of Ti-6Al-4V alloy. This paper investigates the impact of different melt track overlap rates on the quality of Ti-6Al-4V samples formed by SLM through a combination of simulation and experimentation. The findings reveal that if the overlap rate is overly small (<14.3%), the powder at the bottom of the overlap zone cannot be fully melted, thereby forming pores. Additionally, the densification effect causes the actual powder spreading thickness to be greater than the theoretical one. Consequently, when the overlap rate is less than 20%, it is challenging to ensure a close bond between the upper and lower melt tracks. Both the simulation and experimental results demonstrate that an excessive melt track overlap rate will lead to grain growth in the overlap zone and reduce the tensile properties of the sample. Thus, both excessive and insufficient overlap rates are detrimental to the density and mechanical properties of the formed sample. The multi-layer and multi-track model established in this study effectively replicates the actual processing conditions. The retention of the temperature field of the first layer makes the simulation of the melt tracks of the second layer more realistic and reliable. This provides a reference basis for accurately predicting the forming quality of SLM using numerical models in the future.