We have examined alloys of composition SmTiFe11-xCox (x = 0,8,11) and DyTiCo11 via transmission electron microscopy. Results indicate the sample without Co to be composed primarily of the body centered tetragonal 1-12 phase with a small amount of α-Fe and Fe2Ti present. With increasing Co content, the frequency of occurence of the 2-17 phase increases. In Sm containing samples, this phase is rhombohedral, while for Dy samples, the hexagonal phase was also found. Correspondingly, we observed an increase in the amount of transition metal-Ti solid solution as the Co concentration increases. In addition, there are orientation relationships between the 1-12 and both 2-17 phases. This is consistent with a coordinate transformation matrix based on the 1-5 structure. Both the 1-12 and 2-17 phases were found to contain antiphase boundaries in annealed samples containing Sm. The 1-12 phase alone contained antiphase boundaries in the DyTiCo11 sample. These and other results are discussed. © 1990.
