MACROSSEGREGATION DURING TRANSIENT UNIDIRECTIONAL SOLIDIFICATION OF METALLURGICAL GRADE SILICON

The main objective of the present work is to study the macrosegregation of impurity elements during the unidirectional solidification of metallurgical grade silicon. A cylindrical ingot was obtained by melting and solidification of metallurgical grade silicon in a resistance furnace. Macrographs and micrographs of the longitudinal section of the ingot were examined. These reveal a grain structure consisting mainly of columnar grains and intermetallic precipitates concentrated at the ingot top. The remaining part of the ingot was free from any type of intermetallic. The compositions of samples extracted along the ingot were measured by chemical analysis, enabling the construction of concentration profiles. These profiles show an accumulation of impurity elements at the ingot top, indicating the macrosegregation of these elements and an effect of refining the initial composition