Effect of texture on tensile, fatigue and dwell fatigue behavior of commercially pure titanium

The ambient temperature (~25⁰ C) dwell sensitivity of titanium alloys is now a well-known phenomenon. In this work, the normal and dwell fatigue response of commercially pure titanium (cp-Ti) is investigated. Due to the highly anisotropic elastic and plastic response of hexagonal crystals, mechanical behavior of polycrystalline commercially pure titanium is highly dependent on its crystallographic texture. In this study, cold rolled and annealed sheets of cp-Ti was prepared to get a grain size of ~10μm with a split-TD (Transverse Direction) type texture. Tensile, normal fatigue and dwell fatigue response of samples cut along the rolling direction (RD) and the transverse direction (TD) were investigated. Anisotropy in strain rate sensitivities were also investigated using stress relaxation tests. The tensile, fatigue and dwell fatigue responses were observed to be highly texture sensitive. This was correlated with the monotonic strain hardening response and rate sensitivities. Postmortem analysis using scanning electron microscopy (SEM) and electron back scattered diffraction (EBSD) based slip trace analysis revealed interesting aspects related to micromechanisms of plastic deformation during tensile, fatigue and dwell fatigue loading. Viscoplastic self-consistent (VPSC) simulations have been performed to explain the observed texture dependence in the tensile, fatigue and dwell fatigue response.

Keywords: Texture, cp-Ti, Fatigue, Dwell fatigue, Rate sensitivity, SEM, EBSD, VPSC.