Simulation and experiment investigations on fabrication of Fe-based amorphous powders by a novel atomization process equipped with assisted gas nozzles

Based on computational fluid dynamics method, the effect of atomization gas pressure on the atomization efficiency of Laval nozzle was studied, and then a discrete phase model was established and combined with industrial trials to study the effect of a new type of assisted gas nozzles (AGNs) on powder size distribution and amorphous powder yield. The results show that increasing the atomization pressure can effectively improve the gas velocity for the Laval nozzle; however, it will decrease the aspiration pressure, and the optimal atomization pressure is 2.0 MPa. Compared with this, after the application of AGNs with the inlet velocity of 200 m s(-1), assisted gas jet can increase the velocity of overall droplets in the break-up and solidification area by 40 m s(-1) and the maximum cooling rate is increased from 1.9 x 10(4) to 2.3 x 10(4) K s(-1). The predicted particle behavior is demonstrated by the industrial trails, that is, after the application of AGNs, the median diameter of powders d(50) is decreased from 28.42 to 25.56 mu m, the sphericity is increased from 0.874 to 0.927, the fraction of amorphous powders is increased from 90.4% to 99.4%, and only the coercivity is increased slightly due to the accumulation of internal stress. It is illustrated that the AGNs can improve the yield of fine amorphous powders, which is beneficial to providing high-performance raw powders for additive manufacturing technology.