Session *BB2.7

4:00 PM *BB2.7
TRANSPORT PHENOMENA IN DROPLET BASED MANUFACTURING PROCESSES. Enrique J. Lavernia, Department of Chemical Engineering and Materials Science, Department of Mechanical and Aerospace Engineering, University of California, Irvine, CA.

In an effort to optimize the microstructure and physical properties of advanced structural materials, such as composites, a variety of novel manufacturing techniques have evolved over the past few decades. Among these, thermal spray processes offer the opportunity to combine the benefits associated with fine particulate technology (e.g., microstructural refinement, alloy modifications, etc.,) with in-situ processing, and in some cases, near-net shape manufacturing. The manufacture of composite coatings using droplet processes, for example, typically involves the mixing of reinforcements and matrix under highly non-equilibrium conditions, and as a result, these processes offer the opportunity to modify the properties of existing alloy systems, and develop novel alloy compositions. In principle, such an approach will inherently avoid the extreme thermal excursions, with concomitant macrosegregation, normally associated with more classical casting processes. Furthermore, droplet based processes also eliminate the need to handle fine reactive particulates, normally associated with powder metallurgical processes. In the present lecture, the interrelationship between transport phenomena and the resulting microstructure and mechanical behavior of various thermal sprayed materials are highlighted and discussed. The nucleation phenomena that are associated with the co-injection of ceramic particulates into atomized metal droplets are studied using finite difference analysis. Classical nucleation theory, together with thermal interactions between particulates and droplet, are then used to predict the onset temperature for nucleation. In addition, recent results pertaining to droplet deformation are discussed and compared to those anticipated from currently available theoretical models, paying particular attention to the synergism between transport phenomena and microstructure.