Insight into the influence of melt superheat on flow field dynamics and particle morphology in gas-atomized Fe-based amorphous alloys: Simulation and experimental

Abstract

Powder morphology exerts a profound influence on the forming quality of additive-manufactured components, which is vastly dependent upon the control of the gas atomization process. This work systematically investigates the impact of melt superheat upon atomization flow field dynamics and particle morphology for Fe-based amorphous alloys across a superheat temperature range of 250–400 K in terms of combined numerical simulations and experiments. A multistage numerical model incorporating secondary breakup and solidification deformation was developed using the realizable k-ε turbulence model, discrete phase model, and volume of fluid method. Results reveal that there is a slight influence on the flow field at lower superheats (250–350 K). Yet, at a superheat up to 400 K, the recirculation zone elongates and the secondary acceleration zone disappears, which leads to an increment in the proportion of fine droplets and a transition in the droplet size distribution from normal to monotonically declining tendency. In the droplet solidification deformation stage, a higher superheat or larger initial droplet diameter appears to enhance the solidification time, beneficial to yield spherical powder. Further, a novel criterion for spherical powder formation was established in relation to the Weber number (We). The experimental data depict that the proportion of spherical powder improves substantially, from 23% to 74%, as superheat rises from 250 to 400 K, closely matching theoretical predictions. This in-depth understanding of powder formation mechanisms in gas atomization provides valuable guidance for optimizing spherical powder yield.