Prediction of solidification behavior of gas-atomized Sn-5mass%Pb droplets

Abstract

Purpose – The aim of the present work is to study the effect of processing conditions on solidification path and resultant microstructure and further predict the solidification behavior of gas-atomized Sn-5mass%Pb droplets. Design/methodology/approach – Combined with previous models for in-flight droplet nucleation and non-equilibrium solidification, a simulation method is applied to four typical containerless solidification conditions with helium, nitrogen or argon gas at two different gas jet velocities, in the presence of 10 or 500 ppm oxygen. The simulation outputs distribution of primary dendrite composition, tip velocity and tip radius with radial distance from the nucleation point, and the fraction solid at the end of recalescence and the post-recalescence duration. Both surface and internal nucleation are considered. The possible dendritic fragmentation in the post-recalescence stage is also discussed. Findings – Result indicates that dendritic fragmentation is not likely to occur in droplets solidifying along the paths considered in the simulation. Originality/value – The simulation method applies to any droplet-based solidification process for which droplet cooling schedule is known and thus provides a scientific basis for powder quality assurance.