Twinning in pure Ti subjected to monotonic simple shear deformation

Abstract

The aim of this paper is to provide a thorough study on the occurrence and importance of deformation twinning in simple shear deformed pure α-Ti. A statistically relevant inspection of the morphology of the deformation twins in relation to the applied strain/deformation is performed. The investigated microstructural aspects are the twin volume fraction, the twin thickness distribution and the resolved shear stress distribution on the twin plane. All these aspects are examined as a function of the twin types and two initial textures. Monotonic simple shear experiments are carried out for three different loading directions with respect to a direction linked to the initial crystallographic texture. EBSD and TEM observations reveal the presence of 101¯2 and 112¯2 twins. The statistical analysis reveals that 101¯2 and 112¯2 twins have a similar average thickness around 1.9 nm, but the 101¯2 twins show a far larger spread on their thickness and can grow to almost the size of the original parent grain. Correlation of the twin fractions with the RSS analysis shows that RSS is an acceptable method explaining the difference in twin fractions for different textures and orientations. A detailed analysis shows that 112¯2 twins occur in average with a smaller volume fraction but with a higher RSS, indicating they are more difficult to nucleate or grow compared to 101¯2 twinning. In general a higher RSS value on the twin plane is not connected to a higher twin thickness; only in the case of 101¯2 twins the highest RSS values show clearly thicker twins.