Tensile properties and work-hardening behavior of Fe-3%Al single crystal

The tensile deformation behavior of single and poly-crystal Fe-3%Al alloys was investigated at room temperature. The work hardening rate (WHR) of the polycrystalline alloy monotonously decreased with increasing strain and increased with decreasing grain size. The WHR of the single crystal alloy was remarkably lower than that of the polycrystalline alloy, and the single crystal alloy exhibited a peculiar behavior that could be classified into four different types depending on the tensile axes. When the tensile axes were on the line connecting <102> and <101> in the stereo triangle, the characteristics of deformation of the single crystal alloy were steady and its WHR showed a monotonous decrease similar to that observed in the case of the polycrystalline alloy. For most of the tensile orientations, including <001>, the WHR curve changed from concave to convex with a strain increase. The WHR for the <101> orientation also showed the maximum and minimum values, i.e., it dropped immediately after reaching the maxima. This behavior was considered ascribable to the transition of the dislocation structure. The deformation for the <111> orientation was characterized by the highest yield stress and work softening, which were caused by some intense slip bands with discontinuous stress drops. Lattice rotation with tensile deformation in single crystal alloys was also examined by an electron backscatter diffraction (EBSD) measurement. For determining the rotation direction, the stereo triangle was divided into two areas by a great circle connecting <113> and <102>.