Discipline: Technology and Engineering
Subcategory: Materials Science
Felicia Rutland - North Carolina Agricultural & Technical State University
Co-Author(s): Taher Abu-Ledbeh and Genaro Pérez-de León, North Carolina Agricultural & Technical State University, Greensboro, NC Roland Seals and Vincent Lamberti, Y-12 National Security Complex, Oak Ridge, TN
Gas Atomization (GA) is a method to produce spherical powders of metal alloys. In the process, a stream of molten metal is introduced to high pressure or high velocity gas, forming droplets which solidify while falling through an inert environment, resulting in spherical powder particles. Processing parameters affect the thermal history and cooling rate experienced by gas-atomized powders, and thus simulation, and analysis, of these phenomena provide procedure optimization opportunities. During GA, solidification is completed over an extremely short range of time, milliseconds in certain cases. Accurately recording temperature variations and cooling rates of micro-sized powders is not possible over short time spans and under the conditions that the powders are formed. Optimization is an important part of powder production because it allows for ideal powder formation under particular restraints. Excellent research on GA simulation is available, but no published numerical studies on thermal behavior and process optimization exist regarding Uranium metal. Our research involved developing a model that examined the effects of gas-to-metal ratio (GMR), droplet size, gas and metal superheat temperatures, and gas-droplet relative velocities on Uranium droplets. The purpose of the model is to provide fundamental insight into the thermal and velocity profiles experienced by gasatomized Uranium powders, and to utilize this information to optimize processing parameters. The results show that with decreasing droplet size, a larger cooling rate is experienced. For a given constant nozzle orifice, increasing GMR results in increased cooling rate. Larger superheat temperatures also led to higher cooling rates. Future research will involve comparing experimental studies with the simulation data to optimize the model. Also, the understanding of the relationship between GA processing, thermal behavior and powder microstructure evolution will be developed.
Funder Acknowledgement(s): Y-12 National Security Complex (Y-12) / Minority Serving Institution Partnership Program (MSIPP).
Faculty Advisor: Taher Abu-Ledbeh,