Finite Element Prediction of Residual Stress in Rhombic Dodecahedron Ti-6Al-4V Titanium Alloy Additively Manufactured by Electron Beam Melting

In this work, a three-dimensional nonlinear transient thermo-mechanically coupled finite element model (FEM) is established to investigate the variation in temperature and stress fields during electron beam melting (EBM) of rhombic dodecahedron Ti-6Al-4V alloy. The influence of the processing parameters on the temperature and residual stress evolutions was predicted and verified against existing literature data. The calculated results indicate that the interlayer cooling time has very little effect on both the temperature and stress evolutions, indicating that the interlayer cooling time can be set up as short as possible to reduce manufacturing time. It is presented that the residual stress of the intersection is higher than that of non-intersection. With increasing preheating temperature, the residual stress decreases continuously, which is about 20%-30% for every 50 degrees C rise in temperature. The temperature and stress fields repeated every four layers with the complex periodic scanning strategy. Both x and y-component residual stresses are tensile stresses, while z-component stress is weak compressive or tensile stress in typical paths. It is proposed that the interlayer cooling is necessary to obtain a rhombic dodecahedron with low residual stress. These results can bring insights into the understanding of the residual stress during EBM.

Automated summary

A three-dimensional nonlinear transient thermo-mechanically coupled finite element model was established to investigate the variation in temperature and stress fields during electron beam melting of rhombic dodecahedron Ti-6Al-4V alloy. The influence of processing parameters on temperature and residual stress evolutions was predicted and verified. The results show that interlayer cooling time has little effect on temperature and stress evolutions, indicating its minimization for reducing manufacturing time. The study also highlights the importance of interlayer cooling for obtaining low residual stress in the rhombic dodecahedron structure.