Misorientation characteristics and textural changes induced by dense twins in high-purity Ti sheet after small strain rolling

Abstract

A high-purity Ti (HP-Ti) sheet was subjected to small strain rolling (10% reduction) with microstructural and textural characteristics examined by electron channeling contrast imaging and electron backscatter diffraction techniques. Particular attentions were paid to misorientation and textural changes aroused by twins in the rolled HP-Ti sheet. Results show that after the 10% rolling, almost all the prior equiaxed grains in the initial specimen are twinned, leading to remarkable grain refinement. The presence of two major misorientation angle peaks around 65° and 85° is ascribed to {11–22} and {10–12} twinning, respectively, and two minor peaks around 47° and 77° are due mainly to impingement of various variants of such twins. Distinct from earlier work, the small strain rolling is confirmed to be able to induce drastic textural changes in pure Ti sheets: largely reduced texture intensity and appearance of new textural components. This can essentially be attributed to enhanced twinning activity due to much lower impurity contents of the present material. Primary {11–22} twins are mainly responsible for the new textural component of c-axes aligned near the rolling direction with spread, while the component of c-axes parallel to the normal direction is due to reorientation of secondary {10–12} twins. This study clearly demonstrates the capability of small strain rolling to effectively modify both microstructures and textures of the HP-Ti sheet and may shed some light on exploring feasible processings for such materials.