Sammendrag
Three 12 kg ingots were grown using both standard slip cast crucible and standard coating as well as ultra clean crucible and coating. Also the conditions during crystallisation were varied. The ingots were characterised for lifetime and dislocation density. The ingots made using ultra clean coating and crucibles showed higher lifetime than the standard ingot. One of these also had very low dislocation density, and the as grown lifetime of this ingot reached ~130 µs. The two ingots with lower dislocation density both showed long linear features in the bottom wafers. When studied in EBSD it appears that the high lifetime ingot was dominated by <211> and <111> oriented grains, which probably are a result of dendritic nucleation. The wafer from the ingot with poor lifetime also was dominated by few, although different orientations. We believe the lower dislocation density is related to the nucleation phase. Two models that can explain this feature were discussed.