| Author(s): |
Martorano, Marcelo A.
;
Ferreira Neto, Joao B.
;
Oliveira, Theogenes S.
;
Tsubaki, Tomoe
;
TMS
Total Authors: 5
|
| Document type: | Journal article |
| Source: | TMS2011 SUPPLEMENTAL PROCEEDINGS, VOL 1: MATERIALS PROCESSING AND ENERGY MATERIALS; v. N/A, p. 8-pg., 2011-01-01. |
| Abstract | |
Directional solidification of metallurgical-grade Si was carried out in a vertical Bridgman furnace. The effects of changing the mold velocity on the macrosegregation of impurities were investigated. Macrostructures of cylindrical Si ingots consist mostly of columnar grains parallel to the ingot axis. Neither dendrites nor cells were observed, although there is some indication of their presence in the microstructures obtained at the largest velocities. Measured concentration profiles of impurities showed that ingot bottom and middle are purer than the metallurgical Si. Impurities accumulated at the ingot top, creating a typical normal macrosegregation. When mold velocity decreases, macrosegregation and ingot purity increase, changing abruptly below 20 mu m s(-1). A mathematical model of solute transport shows that, for mold velocities >= 20 mu m s(-1), macrosegregation is caused mainly by diffusion in a stagnant liquid layer assumed at the solid-liquid interface, while for lower velocities, macrosegregation increases owing to convective solute transport. (AU) | |
| FAPESP's process: | 03/08576-7 - Modelagem matematica da solidificacao de ligas binarias sob efeito de conveccao natural no liquido e movimentacao da fase solida. |
| Grantee: | Marcelo de Aquino Martorano |
| Support Opportunities: | Research Grants - Young Investigators Grants |
| FAPESP's process: | 03/14118-1 - Refino do silicio por solidificacao direcional. |
| Grantee: | Joao Batista Ferreira Neto |
| Support Opportunities: | Regular Research Grants |