The influence of dynamic strain aging (DSA) on low cycle fatigue (LCF) in duplex Ti-6-4 and SP700 titanium alloys was studied. LCF was performed within the temperature range from 350 degrees C to 450 degrees C, at strain rates of 10(-3) s(-1) and 10(-4) s(-1), and strain amplitudes of 1.25% and 2%. DSA appeared as serrations at the plastic portion of the cyclic stress-strain hysteresis loop, as well as stress humps appearing in the cyclic stress response (CSR) curve of peak tensile stress response versus cycle number. Strain-induced micro twin formation was only observed in the sample after fatigue with 2% strain amplitude under a 10(-4) s(-1) strain rate, indicating that it is a DSA induced phenomenon. (C) 2011 Elsevier B.V. All rights reserved.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING