Deformation Behaviour of Titanium in Torsion

Abstract

The evolution of microstructure and texture in Hexagonal Close Pack commercially pure titanium has been studied in torsion in a strain rate regime of 0.001 to 1 s-1. Free end torsion tests carried out on titanium rods indicated higher stress levels at higher strain rate but negligible change in the strain-hardening behaviour. There was a decrease in the intra-granular misorientation while a negligible change in the amount of contraction and extension twins was observed with increase in strain rate. The deformed samples showed a C1 fibre (c-axis is first rotated 90° in shear direction and then +30° in shear plane direction) at all the strain rates. With the increase in strain rate, there was an increase in the intensity of the C1 fibre and it became more heterogeneous with a strong {11 6} component. In the absence of extensive twinning, pyramidal slip system is attributed for the observed deformation texture. The present investigation, therefore, substantiates the theoretical prediction of increase in strength of texture with strain rate in torsion.