A novel yielding anisotropy and corresponding lattice evolution mechanism in CP-Ti achieved via pulsed electric current

We report a novel yielding anisotropy in commercially pure titanium (CP-Ti) and provide fundamental insights into its texture evolution and the corresponding lattice evolution mechanism. Herein, yielding anisotropy was attained by an alpha <->beta cyclic phase transformation (CPT) treatment via pulsed electric current (PEC). After the three-cycle CPT treatment, the CP-Ti perpendicular to the PEC direction exhibited the maximum value of (0002) plane in the X-ray diffraction intensity and of {0001} pole figure for electron backscatter diffraction analysis. The three-cycle-treated CP-Ti presented a significant yielding anisotropy which was the far greater yield strength (297.5 MPa) than that of the other treated specimens. This is attributed to the preferential activation of basal < a > slip with a higher effective critical resolved shear stress in the three-cycle-treated CP-Ti, compared with the preferential activation of prismatic < a > slip for the other treated specimens. Fundamentally, the lattice evolution mechanism and orientation relationship ({0001}(alpha)// {001}(beta) and < 11 (2) over bar0>(alpha)// <<(1)over bar>00>beta) responsible for this yielding anisotropy were proposed. Under the PEC, the (0001) plane in HCP structure transformed in parallel to the (001) plane in BCC structure, and followed by the transformation of the (110) plane in the BCC to the (0001) plane in the HCP under cooling when the PEC was switched off. (c) 2021 The Author(s). Published by Elsevier Ltd.

Automated summary

A novel yielding anisotropy in commercially pure titanium (CP-Ti) was achieved through alpha <->beta cyclic phase transformation (CPT) treatment using pulsed electric current (PEC). The CP-Ti exhibited significant yielding anisotropy after the three-cycle CPT treatment, with a much higher yield strength than other treated specimens. The lattice evolution mechanism and orientation relationship responsible for this yielding anisotropy were proposed, highlighting the preferential activation of basal <a> slip in the three-cycle-treated CP-Ti.