Low-cycle fatigue behaviors of commercial-purity titanium

Low-cycle fatigue behaviors of commercial-purity titanium (TA2) were investigated under constant total strain amplitude control at room temperature in air. It was found that commercial-purity titanium exhibited a complex cyclic hardening behavior over the strain range 0.5–2.4%. By optical microscope (OM) and Image Scan Analyzer, the cyclic deformation twins were observed and the quantitative relations of twin fraction FT versus strain amplitudes and cyclic numbers were proposed. Meanwhile, the dislocation structures in cyclically deformed commercial-purity titanium were observed by transmission electron microscopy (TEM). In combining the observations of dislocation patterns and deformation twins, a microstructure evolution map was given. On the basis of the experimental results, the effect of microstructures (including deformation twins and dislocation patterns) on the cyclic stress–strain response was discussed.