MODELING AND MICROSTRUCTURE DEVELOPMENT IN SPRAY FORMING

Models of the spray forming process from different groups shaw reasona ble agreement with each other and with the real process, Use of these models has provided considerable insight into the several complex proc esses involved in spray forming; in addition, the models allow designe d experiments to provide further insight into the process. In the work described it has been shown that the modeled fraction of liquid in th e spray f(l)(s) appears to be an appropriate control parameter for spr ay The differences forming. Sticking efficiency and porosity have been found to correlate well with f(l)(s). The differences found in the op timum value of the fraction of liquid in the spray for billets (0.3) a nd tubes (0.5-0.6) indicate, however, that the actual control paramete r may be the fraction liquid in the deposit, f(l)(d) on the surface un der the spray. The need for improved modeling, particularly of the ful l thermal profiles in complex geometries such as spray deposited tubes , is discussed as is the value of improved process diagnostic tools fo r direct experimental measurement of such features as droplet sizes an d velocities, and the deposit temperatures in actual spray forming pro cesses.