Parameter analysis of thermal behavior during laser melting of Ti-6Al-4V alloy powder

The additive manufacturing temperature field of Ti-6Al-4V powder laser melting (LM) with a direct-diode laser source is simulated by the finite element method (FEM). How the laser power and scanning velocity affect the thermal behavior of LM is discussed. The results show that the cooling rate of the molten bath increases from 88.7 to 103.3 °C/s when the laser power rises from 3000 to 3500 W. However, when the laser moving velocity rises from 3 to 7 mm/s, the cooling rate drops from 95.8 to 74.3 °C/s. When both the low laser power (3250 W) and high laser moving velocity (7 mm/s) are chosen, the low temperatures (1408 °C) and very short liquid-phase life are produced, resulting in poor wettability of the molten pool and micropores in the parts. The bath depth rises from 1.7 to 4 mm when the laser power increases from 3000 to 3500 W. As the laser moving velocity increases from 3 to 7 mm/s, the bath depth is reduced from 4.1 to 1.9 mm. When the laser power is equal to 3500 W and the laser moving velocity is 5 mm/s, the bath with a width of 6.5 mm and a depth of 4 mm is successfully achieved. At the same time, the laser cladding Ti-6Al-4V alloy experiment is performed with the same process parameters as the simulation process. The sample microstructure from the experiment is studied and the results show that the simulation model is effective.