Accession Number : ADA310665

Title :   Modeling for Microstructural Control in Spray Forming.

Descriptive Note : Final rept. for 1989-1995,

Corporate Author : DREXEL UNIV PHILADELPHIA PA DEPT OF MATERIALS ENGINEERING

Personal Author(s) : Doherty, Roger D. ; Mathur, P. ; Annavarapu, S. ; Cai, Cheng

PDF Url : ADA310665

Report Date : JUN 1996

Pagination or Media Count : 170

Abstract : The earlier 'Drexel' model of Spray Forming was modified with improved measurements of the atomization process: particle size distribution, radial mass flux and gas velocity field as a function of process parameters. The model was also extended to predict, successfully, the droplet undercoolings, the deposit shapes and, in a two dimensional model, the temperatures in the deposit. (A three dimensional thermal model was started but not completed under this funding) Experiments, designed using the model, showed that the droplet sticking efficiency rose and the deposit porosity fell as the fraction liquid in the spray increased from 0.1 to 0.3 for billets and from 0.2 to 0.5 for tubes. Thermal models indicated that the fraction liquid in the deposit approached that in the spray for billets but fell below that in the spray for tubes. The results show that fraction liquid (ideally on the top surface of the deposit) is the best control parameter for spray forming. Grain sizes in the deposit closely tracked the solidification times but showed a slower coarsening rate (a smaller grain size) than expected from both experiments in pure materials and as modeled here. The discrepancy arose from inhibition of grain growth, in the solid-liquid state, by extrinsic impurity phases, often nitrides produced during gas atomization. p1

Descriptors :   *CONTROL, *PARTICLE SIZE, *MICROSTRUCTURE, *MODELS, *SOLIDIFICATION, *DROPS, *SPRAYS, *ATOMIZATION, THERMAL PROPERTIES, VELOCITY, DISTRIBUTION, PARAMETERS, TWO DIMENSIONAL, MATERIALS, FLUX(RATE), SHAPE, COPPER ALLOYS, GRAIN SIZE, IMPURITIES, POROSITY, NITRIDES, PHASE, GASES, SURFACES, THREE DIMENSIONAL, DEPOSITS, PURITY, MASS FLOW, TITANIUM, GRAIN GROWTH, LIQUID METALS.

Subject Categories : Physical Chemistry
      Inorganic Chemistry
      Properties of Metals and Alloys
      Crystallography
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE