An integrated simulation model towards laser powder bed fusion in-situ alloying technology

Abstract

The Laser Powder Bed Fusion (LPBF) in-situ alloying is a novel technology for preparing novel alloys efficiently. However, the narrow process window limit its application. A micro-scale integrated simulation model is designed and constructed based on the Discrete Element Method (DEM), the Finite Element Method (FEM), and Calculation of phase diagram (CALPHAD) method in the work. The equation of the methods are introduced. By defining the parameters such as composition inhomogeneity ω, the forming performance of LPBF in-situ alloying FeCoCrNi medium entropy alloys are predicted. The calculation results show that the hysteresis diffusion effect makes the mixing powders more challenging to be in-situ alloyed than conventional main component alloys. For the mixed powder beds consisting of 15–53 μm particles with equal mass ratio, the composition deviation on the micro-scale is within 2.5%, and the composition homogeneity reaches 98.9 %. Under a laser power of 150 W and a scanning speed of 500 mm/s, several laser remelting process are indispensable to eliminate unmelted elements. Experiments are carried out to verify the accuracy of the integrated simulation model, and the high-efficiency preparation experiment of non-equiatomic ratio medium entropy alloy was carried out by using the technology.

Keywords

• Laser powder bed fusion in-situ alloying
• Selective laser melting
• CALPHAD
• Medium entropy alloy
• Integrated calculation