Role of crystallographic orientation on the deformation behaviour of Ti-6Al-4V alloy during low cycle fatigue

ABSTRACT

Low cycle fatigue (LCF) tests were carried out on Ti6Al4V alloy at room temperature for different strain amplitudes ranging from 0.5% to 2%. The microstructure and texture evolutions as a function of strain amplitude have been investigated in the present study. Cyclic softening behaviour was observed at all strain amplitudes, and it was found to increase with increasing the strain amplitude. The fatigue transition life was observed to be at 1.25% strain amplitude. Only $\left(10\overline{1}2\right)$ type tensile twins were formed during the deformation, and this was found to be significant at higher strain amplitude of 2%. The grains along $\left[10\overline{1}0\right]$ were appeared to be the twinning parent, and the twinned products were appeared along [0001]. The $\left[10\overline{1}0\right]$ grains were further found to have substantial cyclic deformation than the other grains, such as $\left[2\overline{1}\overline{1}0\right]$ and [0001]. The dominant texture was found along $\left[10\overline{1}0\right]$ during the LCF tests. However, the sample at higher strain amplitude of 2% had also prominent [0001] texture along with $\left[10\overline{1}0\right]$ texture. Fractographic examination revealed a dimple fracture surface at lower strain amplitude (0.5%), whereas a quasi-cleavage type fracture was observed at higher strain amplitudes (1% & 2%).

KEYWORDS:

• Ti-6Al-4V
• low cycle fatigue
• cyclic softening
• back stress
• friction stress
• EBSD
• texture

Acknowledgements

The authors thank Prof. I. Samajdar for conducting EBSD measurements of the samples in his laboratory, National Facility on OIM and Texture, at Dept. of Metallurgical Engg. and Materials Science, IIT Bombay, Powai, Mumbai. The authors also acknowledge the DST-FIST supported XRD-Texture laboratory at Dept. of Metallurgical & Materials Engg., NIT Rourkela, for texture analysis of the samples.

Disclosure statement

No potential conflict of interest was reported by the author(s).