Finite Element Simulation and Experimental Validation of the Thermomechanical Behavior in Selective Laser Melting of Ti55531 Alloy

The finite element model was established to predict the thermal and stress fields in selective laser melting of Ti55531 alloy. The temperature distribution, melt pool dimension, and solidification parameters on the different scanning speeds were evaluated and analyzed. The results show that the temperature and dimension of the melt pool decrease as the scanning speed increases. The maximum cooling rate and solidification rate are about 1.38 × 104 ℃/s and 0.95 mm/s, respectively, obtained at scanning speed of 1000 mm/s, while the minimum cooling rate and solidification rate are approximately 5.80 × 103 ℃/s and 0.2 mm/s, respectively, obtained at scanning speed of 200 mm/s. Relatively high scanning speed improves the instability of the solid/liquid interface and is beneficial for obtaining fine grains. In addition, the thermal stress exhibits a tendency to increase with the laser moves forward, and the residual stress increases sharply mainly during the cooling period. The maximum residual stress reached 878 MPa with a scanning speed of 1000 mm/s. The simulations and experiment results exhibit good agreement. A surface heat source with Gaussian distribution was used to realize the numerical simulation of SLM under different scanning speeds, which provides a good reference for the optimization of deposition parameters of Ti55531 alloy and the production of good-quality deposited components in the future.