Role of deformation twin on texture evolution in cold-rolled commercial-purity Ti

Abstract

Texture evolution of a commercial-purity titanium (CP-Ti) during cold rolling was studied by means of x-ray diffraction (XRD) and electron back-scattered diffraction (EBSD). Twinning was identified to significantly contribute to deformation up to reductions of about 50%. Based on initial texture of the material investigated and twinning modes available in hexagonal close-packed (HCP) structures, the measured texture evolution can be interpreted in terms of (i) compressive twinning ({11¯22}〈11¯2¯3〉) within the two dominant initial texture components B ({0001}〈10¯10〉±40°TD) and E ({0001}〈11¯20〉±40°TD) and (ii) followed by tensile twinning ({10¯12}〈10¯1¯1〉) in the then-favorably reoriented twinned part. Reduction of grain size at high deformation inhibits further twinning and results in a stable texture evolution driven exclusively by dislocation slip. During cold rolling, the crystals of the initial texture component B first rotate to orientation M ({01¯10}〈2¯1¯12〉) by compressive twinning (primary), and then orientation M rotates to orientation D ({0001}〈11¯20〉) by tensile twinning (secondary). Meanwhile, the crystals of the initial component E first rotate to the orientation M′ ({14¯53}〈6¯5¯13〉) by compressive twinning (primary), and then orientation M′ rotates to the orientation A ({0001}〈10¯10〉) by tensile twinning (secondary). At higher deformation level, twinning was significantly depressed by strongly refined grain size, which resulted in the elimination of the transient texture components caused by slip. These results are useful for the prediction and control of the texture in titanium.