Effect of temperature on elastic constants and dislocation properties of Fe 30% Al single crystals

The elastic constants of Fe 30% Al single crystals were determined using a resonance technique over the temperature range, 293–1173 K, of the observed yield strength anomaly. While the elastic shear anisotropy, Zener's factor, is high, A = 4.6–6.8, the factor related to a shear with respect to the 〈111〉 direction is rather low, M = 1.2–1.3, over the temperature range. The elastic anisotropy factors for dislocation width calculated for the edge and screw orientations of the {110}〈111〉 slip give the ratio of K eS 66/K eS 44 = 2.4 at 773 K, suggesting that the mobility is significantly higher for edge than for screw character. In the absence of applied stress, a coplanar dissociation of two 〈111〉/4 screw partials with the APB partly lying on {110}, and partly on {112}, is not likely in Fe-30% Al. For a more detailed study of dislocation micromechanics to explain deformation behavior of Fe-30% Al, discussion is given on the anisotropy of APB energies, the relationship of non-Schmid effect with the anisotropic coupling coefficients, and possible glide resistance associated with the unstable orientation of dislocation line tension.