Growth interface and dislocation structure of single crystals of iron and dilute iron-silicon alloys

Abstract

Dislocation in as-grown crystals and in the vicinity of the growing interface were investigated in crystals of Fe, Fe-0.5 wt% Si and Fe-0.9 wt% Si prepared by the strain-anneal method. It was found that the dislocation density close to the interface was much lower than in the as-grown crystal, indicating that the main part of dislocations originates in the as-grown crystal, probably due to thermal and other stresses. Groups of dislocations with higher density observed at some places in crystals with low average dislocation density, remain at those places, where grains in the polycrystalline specimen have the same orientation as the growing crystal. The density of dislocations in dilute iron-silicon alloy single crystals was found to be lower than in pure iron crystals. This is supposed to be due to higher resolved shear stress necessary to produce dislocations in Fe-Si alloys compared to that for pure iron.