DISLOCATION STRUCTURE IN "AS-GROWN" HIGH-PURITY IRON SINGLE CRYSTALS

The dislocation structure in iron single crystals prepared by two different strain–anneal techniques from the starting material of two different purities is studied by the method of etch pits. Average dislocation densities of 2.6 × 105 to 7 × 105 cm−2 and the absence of subboundaries are observed in single crystals grown statically or dynamically from zone-refined Johnson and Matthey spectrographic iron. The presence of broad subboundaries and average dislocation densities of 8.6 × 105 to 3.3 × 106 cm−2 is characteristic for single crystals grown from the non–zone-refined J. and M. iron. Annealing of "as-grown" crystals does not greatly influence the dislocation structure. It is assumed that the impurities are mainly responsible for the observed dislocation densities.