Work hardening in Fe-Al alloys

Work hardening in polycrystalline Fe-Al alloys has been examined for alloys containing from nearly no Al up to about 40 at.% Al. A sharp maximum in work hardening is seen for alloys containing 26-30% Al. Examination of dislocation structures with increasing Al content over the region of the maximum shows that the most important change, apart from the formation of superdislocation dipoles instead of single dislocation dipoles, is the predominance of straight screw dislocations and the formation of sessile dislocation segments by reactions of mobile dislocations. The peak in work hardening rate coincides with increased elastic anisotropy, but this is believed to reflect the importance of core/Peierls effects rather than to be a direct cause of high work hardening. (C) 2007 Elsevier B.V. All rights reserved.