In situ observations of detwinning and strain localization in pure titanium

Abstract

In situ scanning electron microscope (SEM) and electron back scattering diffraction (EBSD) are used to investigate detwinning deformation of pre-twinned titanium under uniaxial tension. An electro-polishing procedure is optimized to prepare SEM speckles on the Ti samples with minimum interference with EBSD characterization. Strain fields are obtained from the SEM images via digital image correlation. The experimental results suggest that the rate of detwinning decreases with increasing plastic strain, and detwinning deformation is governed by the Schmid’s law. Strain localization mainly occurs in the detwinning regions during the early deformation. As deformation proceeds, localized plastic strain tends to accumulate rapidly around the {101‾2} extension twins with a low Schmid factor. However, the strain values inside the {101‾2} extension twins are relatively low, regardless of their Schmid factors and the applied tensile strain level.