By means of a direct-current electrodeposition technique, bulk (similar to 3 mm in thickness) polycrystalline Cu samples with preferentially oriented nanoscale twins have been synthesized. Strain-controlled pull push fatigue tests of the nanotwinned Cu samples show that the cyclic stability is maintained after a short initially rapid cyclic hardening stage, distinct from continuous cyclic softening of ultrafine-grained Cu. The saturation stress increases with increasing strain amplitude and decreasing twin thickness, while the longer low cycle fatigue life is achieved at larger grain size. The strain life and S-N curves reveal that the preferentially oriented nanotwins embedded in microsized grains enhance the low and high cycle fatigue property synergy for nanotwinned Cu, which has better low cycle fatigue life while maintaining higher endurance limit (90 MPa at 10(7)), compared with that of coarse-grained Cu and ultrafine-grained Cu. Besides the relatively stable microstructure, the activation of a single primary slip system, i.e. threading dislocation propagation inside nanoscale twin lamellar channels, dominates the steady state of nanotwinned samples. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
[pan, q. s.
; lu, l.] chinese acad sci, inst met res, shenyang natl lab mat sci, shenyang 110016, peoples r china.
; lu, l (reprint author), chinese acad sci, inst met res, shenyang natl lab mat sci, shenyang 110016, peoples r china.