The low-cycle fatigue behavior of an Al–Mg–Sc alloy containing coherent Al3Sc particles with average diameters 4 and 11nm was examined under constant plastic-strain amplitudes in the range of 1.0 x 10−4 to 5.0 x 10−3. Although the coherent Al3Sc particles were shearable, no cyclic softening was observed in specimens with large particles of 11nm. Specimens with small particles of 4nm showed cyclic softening at plastic-strain amplitudes higher than 1.0 x 10−3. In the large-particle specimens, dislocations were uniformly distributed under all applied plastic-strain amplitudes, whereas the small-particle specimens, in which the cyclic softening occurred, exhibited clearly developed slip bands. The cyclic softening could be explained by a loss of particle strength through particle re-dissolution within strongly strained slip bands.

Low-Cycle Fatigue Behavior and Dislocation Structure of an Al–Mg–Sc Alloy. C.Watanabe, C.Y.Jin, R.Monzen, K.Kitagawa: Materials Science and Engineering A, 2004, 387-389, 552-5