Fatigue fracture behavior of a single-slip-oriented Fe-35 wt.% Cr alloy single crystal containing fine-scale Cr-rich precipitates

The fatigue fracture behavior of a [(1) over bar 4 9] single-slip-oriented Fe-35 wt.% Cr alloy single crystals containing fine-scale Cr-rich precipitates is investigated at constant plastic strain amplitudes (epsilon(pl)) ranging from 5.0 x 10(-4) to 5.0 x 10(-3) at ambient temperature in air. In the early stage of cyclic deformation, the initial primary crack nucleates at the specimen surface and develops along the primary slip band. With further cycling the deflection of the primary crack takes place into the nearby soft regions, and eventually the zigzag primary crack forms roughly along the primary slip plane ((1) over bar 0 1), accompanied with a few secondary cracks formed in soft regions. In addition, the fracture surface seems to become more brittle-like with increasing epsilon(pl). It is suggested that such a fatigue fracture behavior is mainly bound up with the enhanced strain localization resulting from the dissolution of fine Cr-rich precipitates during cycling, and also with the special macroscopic state of stress, namely, the primary slip plane ((1) over bar 0 1), which makes an angle of 45 degrees with the stress axis, [(1) over bar 4 9], is exactly a maximum shear stress plane. (C) 2007 Elsevier B.V. All rights reserved.