Controlling the solidification process parameters of direct energy deposition additive manufacturing considering laser and powder properties

Abstract

Laser-particle interaction is a distinct characteristic of direct energy deposition additive manufacturing (DED-AM). Integration of the laser-particle interaction and moving heat source model is necessary to determine the relationship between the particle/laser properties and the thermal process, and it can be further combined with a phase-field model. A modified double-ellipsoidal heat source model was proposed to simulate the temperature variations in DED-AM with consideration of the laser and powder properties. The powder particles were generated by a discretized element method. The laser beam was expressed into an electromagnetic wave form, and subsequently, the laser–particle interaction was examined by using the solutions to Maxwell’s equations. A reduction coefficient was then calculated and introduced into the double-ellipsoidal heat source model for simulating temperatures. The phase-field model was combined with the established thermal model to simulate the solidification process in DED-AM. The results indicate that the formed equiaxed grains near the side surfaces of the produced specimen can become finer with an increase in the laser power, which is caused by the increase in the temperature gradient in this region. The equiaxed grains increase with the decrease in the scanning speed owing to the increased temperature gradient during solidification. However, the columnar grains were observed to be hardly affected by the change in the scanning speed, which was also observed in the experiments.