Numerical simulation of the melting and alloying processes of elemental titanium and boron powders using selective laser alloying

Titanium Diboride (TiB2) has excellent performances in terms of hardness, mechanical strength, wear resistance, and corrosion resistance, but its application is still limited due to its poor manufacturability. Selective Laser Additive Manufacturing using elemental powders of Titanium and Boron provides a transforming technology for the application of TiB2 by enabling its 3D free forming capability. In this paper, to investigate the joint effects of selective laser melting and chemical reactions in the Selective Laser Alloying (SLA) process, a numerical based simulation was conducted using COMSOL Multiphysics 5.4. This is the first successful numerical study of melting and reaction in the selective laser alloying process providing details about the molten pool. The influences of the evolution of free solid-liquid interface, species transport, the chemical reaction rate, and the evaporation latent heat were discussed by considering the production of TiB2 and its concentration distribution in the computational domain. The simulation results show that the melting front of the free surface has a relatively high velocity, at the instant when the powder particles melt, the first speed jump will occur, and when the reaction is triggered, the second speed jump will occur; the heat released from the exothermic reaction between Titanium and Boron is an important energy source which can reduce the energy input and help improve the manufacturing efficiency of the SLA process; the evaporation latent heat also has a significant influence to the temperature field in the computational domain; the concentration distribution of TiB2 strongly relies on the chemical reaction rate and the diffusion coefficient. This study may blueprint a design strategy for the Additive Manufacturing research community by considering to adopt the proposed numerical model, predict the reactions and species concentration, and explore the structures of microscale molten pool and the macroscale defects or so.