Modeling of Dynamic Characteristics in Blue Laser Powder Deposition Additive Manufacturing: from Transient Particle to Steady Molten Pool

Laser Directed Energy Deposition (DED) is an important process for additive manufacturing because of the advantage of high manufacturing speed. 450 nm blue laser has higher absorption rate than traditional infrared laser for highly reflective materials such as Al, Cu. However, it is still unclear how the interaction between the blue laser and powder feeding particles affects the melt pool flow and thus the forming of a track. Here, we perform the simulation analysis of blue laser DED of aluminum alloy with high time resolution and spatial resolution, where a single particle model is built to simulate the transient molten pool under the impact of single particle and a single track model is built to simulate the steady molten pool under the impact of multiple particles, and the models are validated by both in-situ and ex-situ experiments. It is found that insufficient melt pool depth and unmelted powder agglomeration are the main causes of porosity in blue laser DED. The influence of process parameters on the deposition process is investigated, and the suitable process parameters window is found. We verified the superiority of the blue laser for highly reflective materials DED through the simulation models. The current study provides new insights into the mechanism of transformation from powders to track under the action of heat in blue laser DED.