Modeling for Microstructural Control in Spray Forming.
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
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1996
- Accession Number
- ADA310665
Entities
People
- Cheng Cai
- P. Mathur
- Roger D. Doherty
- S. Annavarapu
Organizations
- Drexel University