Abstract:The three-dimensional finite element model of Ti-6Al-4V alloy was established to study the effect of different laser energy densities on the thermal behavior and thermal stress evolution of the selective laser melting multi-layer deposition processat low power density. In this simulation, the thermal-structural indirect coupling method was used to calculate the stress field, and the Sqarse/PCG automatic solver was used to increase its convergence. The study results show that, as the energy density of the laser body increases from 37.04J/mm³ to 74.07J/mm³ atlow power density, the temperature distributions have a similar changing trend. The depth and width of the molten pool first increase and then become stable. The experimental molten pool width and simulation results are basically the same. As the energy density of the laser body increases, the overall residual stress shows a decreasing trend, and the decrementis 6.30%. The surface stress is periodically distributed in a “Stripe” shape, the stress is concentrated in the overlap area of the scanning track, and the stress at the edge of the substrate layer is relatively large. Comparing the results of simulated with the experimental interlayer residual stress, it can be seen that as the volume energy density increases, both of them have the same changing trend, and the maximum deviation is 6.28%. Within theenergy density range of 37.04-74.07J/mm³, the simulated/experimental interlayer residual stressesare inversely proportional to the hardness values after fitting.

Key words: laser volume energy density; SLM; Ti-6Al-4V; thermal stress evolution; interlayer residual stress