Abstract:The tensile plastic deformation behavior of B2-ordered Fe₃Al single crystals at room temperature was systematically investigated. The results show that the mechanical properties are strongly orientation dependent. The plastic elongation of crystals with orientation near ［110］ is as high as 42%. Slip trace analysis shows that although slip planes are found to change among {110}, {112} and {123} with the change in orientations, the initial slip planes in allcases are {110}. Five-stage work hardening curve including four linear stages and one parabolic stage is obtained; but not all stages are observed in the actual deformation of each crystal. In combination with investigations of dislocation substructure, it is found that deformations in stage Ⅰ～Ⅲ are corresponding to the motion of two-fold superdislocations. The higher work hardening rate of stage Ⅱis mainly due to the stronger interactions between primary dislocations and secondary dislocations than those in stage Ⅲ. Deformation in stage  involved is not only the motion of two-fold superdislocations but also the slip of dissociated superpartials with APB traps and the formation of APB tube, both of which are attributed to the hardening. Deformation in stage  Ⅴ is controlled by the cross slip of dissociated superpartials. The dominated softening effect of cross slip reduces the hardening rate and leads to the formation of parabolic stage.

Key words: plastic deformation; B2-order; Fe₃Al; single crystal