Effects of forced convection on the micro and macrostructure of metallurgical grade ingots obtained by unidirectional solidification

Abstract:

The effects of forced convection were investigated on the micro and macrostructure of metallurgical grade silicon ingots obtained by unidirectional solidification imposed by a water-cooled base in contact with a crucible bottom containing the melt. A rotating disk was immersed into the silicon melt to force convection. In the resulting ingots, of 100-mm height, convection increases from 8 to 80 mm the length of a region with clearly aligned columnar grains and free of intermetallic precipitates, indicating enhanced macrosegregation. A heat and mass transfer model indicates that the increase in solute transport caused by forced convection decreases the constitutional super-cooling ahead of the solidification front and, accordingly, increases the stability of a planar solid-liquid interface, free from cells or dendrites. The absence of cells and dendrites may have contributed to increase macrosegregation with forced convection.


Reference:
NASCIMENTO, Denir Paganini; MARTORANO, Marcelo Aquino; FERREIRA NETO, João Batista; LIMA, Moysés Leite de; RIBEIRO, Tiago Ramos. Efeito da convenção forçada na micro e macroestrutura de lingotes de silício grau metalúrgicos obtidos por solidificação unidirecional. In: SEMINÁRIO DE ACIARIA, FUNDIÇÃO E METALURGIA DE NÃO-FERROSOS, 48., 2017, São Paulo. Anais… Rio de Janeiro: ABM WEEK 2017. p. 414-424.

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