Effect of deformation modes on strain hardening behavior of rolling-textured pure titanium

Abstract

The effect of loading direction on flow stress of hot-rolled pure titanium with a transverse split basal texture was investigated at room temperature using uniaxial compression and tensile test. Large variation in flow stress was found for samples of different orientations and loading direction. The major sources of this variation were revealed by measuring area fraction for individual twin modes using electron backscatter diffraction (EBSD) and calculating Schmid factors for all important slip modes. Importantly, the Schmid factors were described in inverse pole figure (IPF) because there are significant variations of starting texture for sample orientation. The Schmid factor analysis and twin data for the wide variety of texture change during test enabled the conclusion to be drawn reliably that higher flow stresses were primarily due to an unfavorable orientation for prismatic <a> slip. A greater proportion of {11-22} or {10-12} twinning was not the sign of higher strain hardening rate increase. Increased strain hardening was observed in only the deformation condition that satisfies greater proportion of twinning and texture component change to unfavorable orientation for prismatic <a> slip. This indicated that reorientation induced by twinning was the main effect that determines the flow stress behavior.