Finite element simulation of residual stress distribution during selective laser melting of Mg-Y-Sm-Zn-Zr alloy

Selective laser melting (SLM) has been confirmed as a promising additive manufacturing technology for the formation of lightweight structural parts of magnesium alloy. However, it is noteworthy that residual stress is easily generated during the SLM process of magnesium alloy, and it will induce cracks to reduce the compactness of formed parts. In this study, a three-dimensional (3D) nonlinear transient thermodynamic coupled finite element model (FEM) was built to analyze the effects of the scanning strategy on the thermal stress evolution and residual stress distribution during the SLM process of Mg-Y-Sm-Zn-Zr alloy. Moreover, six groups of simulation tests were performed based on three different scanning strategies (i.e., successive scanning, island scanning, and orthogonal scanning). The stress values of equal scale specimens produced with the same process parameters were examined to verify the simulation results. The equivalent residual stress was the largest under the use of the successive scanning strategy, as indicated by the results. Using the island scanning, the stress distribution in the island was similar to that of successive scanning, whereas there was a high-stress island close to the interface. Besides, the average S11 and S22 residual stresses were 4.90% and 36.13% lower than that of the successive scanning, respectively. Orthogonal scanning was confirmed as the most effective scanning strategy to reduce residual stress. To be specific, the average S11 and S22 residual stresses were 25.19% and 43.12% lower than that of successive scanning when using the intralayer orthogonal scanning. The simulation and experimental verification results indicated that the maximum equivalent residual stress is the lowest (229 MPa), and the stress distribution was most uniform when orthogonal scanning was performed between 4 × 4 island.