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Abstract
The microstructure and mechanical properties of off-stoichiometric single-crystal Fe2AlMn have been investigated. After casting, the alloy contained two sets of thermal antiphase boundaries, (a/4)⟨111⟩ and (a/2)⟨100⟩, which are attributed to the fact that the compound solidifies into a bcc structure and subsequently orders to a B2 structure and then a L21 structure respectively upon further cooling. Crystals strained under tension at room temperature in air at 1s−1 showed 6% elongation, whereas specimens strained at 1 × 10−5 s−1 showed no elongation, indicating that the compound is sensitive to the testing environment. Fracture occurred on {100} in both cases. Compression tests showed that a yield anomaly was present at intermediate temperatures, with the peak yield strength occurring at about 800 K, which is slightly below the L21–B2 transition temperature of 898 K. The slip systems were found to be ⟨111⟩{110} at room temperature and 800 K. Transmission electron microscopy observations showed fourfold-dissociated ⟨111⟩ dislocations in specimens strained at room temperature but only paired ⟨111⟩ dislocations in specimens strained at the peak temperature. The room-temperature yield strength of quenched specimens increased with increasing quench temperatures from 700 to 1100 K.
Acknowledgements
This work was supported at Dartmouth College by the National Science Foundation, Division of Materials Research, through grant DMR-9812211. Dr Easo George of the Oak Ridge National Laboratory is thanked for providing the cast ingot.