Effect of initial orientation on the tensile properties of commercially pure titanium

Abstract

Effect of crystallographic texture on uniaxial tensile deformation of commercially pure titanium was studied using in situ as well as post-mortem electron backscatter diffraction and elastoplastic self-consistent simulations. Correlation of mechanical properties and strain hardening response with deformation micromechanisms like different modes of slip and twinning was established. Tensile specimens were machined along rolling direction in the plane perpendicular to normal and transverse direction (sample A and C, respectively) as well as along transverse direction in the plane normal to rolling direction (sample B) to obtain different initial texture from cold rolled and annealed plate of commercially pure titanium. Sample B showed higher strength but lower strain hardening rate and ductility than the orientations A and C. It showed extension twinning with lateral thickening while the other samples showed coexistence of extension and contraction twinning. Schmid factor accounted for most of the observed twinning although some contraction twinning in sample A is attributed to the effect of internal stresses. A combination of in situ tensile test in a field emission gun scanning electron microscope with electron backscatter diffraction facility and elastoplastic self-consistent simulations aid in obtaining high-fidelity Voce hardening parameters for different slip and twinning systems in commercially pure titanium. The variation in tensile properties can be explained on the basis of propensity of twinning which tends to provide strain hardening at lower strain but contributes to failure at higher strain.

Keywords:

• Titanium
• tensile testing
• texture
• twinning
• electron back scatter diffraction (EBSD)

Acknowledgements

The authors would like to acknowledge Dr Carlos Tome at the Los Alamos National Laboratory USA. and Dr Ahmed Saleh, University of Wollongong, Australia for providing the EPSC code. Thanks are due to Texture Laboratory at the Advanced Centre for Materials Science, Indian Institute of Technology Kanpur for providing the characterisation facilities used in the present investigation. NPG would like to thank IIT Kanpur for the Initiation Grant and Department of Science and Technology, Government of India for providing financial support via the Science and Engineering Research Board to carry out this research.