Plastic deformation and fracture behavior of a Fe-modified Al₃Ti-base L1₂ intermetallic alloy

The microstructure of the ordered intermetallic alloy with a nominal composition of Al₆₆Fe₉Ti₂₄ is nearly single-phase L1₂ structure, with a few second phase agglomerates at some grain corners. Room temperature compression tests showed that this material exhibits a plastic strain of about 11% at fracture. Final fracture of the compression specimens occurred by a shear-off process along a surface oriented about 45 degrees to the compression axis. Fractographic analysis revealed that the fracture is transcrystalline and the fracture mode is mainly quasicleavage plus tearing. Transmission electron microscopy (TEM) was used to explore its deformation mechanisms. The dislocation density was low after homogenization, but is greatly increased during deformation. The deformation mode was found to be 〈110〉 {111} slip instead of twinning as in Al₃Ti. The a〈110〉 superdislocations dissociated into two partials of a/3〈211〉-type, bounding a superlattice intrinsic stacking fault (SISF) on the {111} slip plane.