DEFORMATION-BEHAVIOR IN L1(0)-TYPE FEPT COMPOUND

Compressive deformation of L1(0),-type FePt compound was performed from room temperature to 873 K in a protective atmosphere. The results show that the yield stress decreases monotonically with increasing temperature. The strain rate sensitivity parameter changes with temperature similarly to that of silver and copper, and does not exhibit a ''near-zero'' phenomenon. This indicates that the temperature-dependent deformation in the studied temperature range is similar to that of f.c.c. metals, and very different from that of L1(0) TiAl. The deformation structure investigated by transmission electron microscopy shows that twinning and slip are the two major deformation mechanisms. The twin system was identified as {111}<112] type. No pseudotwinning was found in this alloy as was the case in TiAl. Two different types of dislocations with Burgers' vectors of(1/2)<110] and <101] were identified. The morphology of these dislocations indicates that the dislocations do not experience a high Peierls' stress as seen in TiAl. No self-dissociation of superdislocations or antiphase boundary cross-slip onto cube planes was observed under weak beam conditions.