Microstructure and Texture Evolution During Sub-Transus Thermomechanical Processing of Ti-6AI-4V-0.1B Alloy;Part I. Hot Rolling in (α + β) Phase Field

摘要

In the current study, the evolution of microstructure and texture has been studied for Ti-6A1-4V-0.1B alloy during sub-transus thermomechanical processing. This part of the work deals with the deformation response of the alloy by rolling in the (a + ft) phase field. The (α + β) annealing behavior of the rolled specimen is communicated in part II. Rolled microstructures of the alloys exhibit either kinked or straight a colonies depending on their orientations with respect to the principal rolling directions. The Ti-6A1-4V-0.1B alloy shows an improved rolling response compared with the alloy Ti-6A1-4V because of smaller a lamellae size, coherency of α + β interfaces, and multiple slip due to orientation factors. Accelerated dynamic globularization for this alloy is similarly caused by the intralamellar transverse boundary formation via multiple slip and strain accumulation at TiB particles. The (0002)o, pole figures of rolled Ti-6A1-4V alloy shows "TD splitting" at lower rolling temperatures because of strong initial texture. Substantial β phase mitigates the effect of starting texture at higher temperature so that "RD splitting" characterizes the basal pole figure. Weak starting texture and easy slip transfer for Ti-6A1-4V-0.1B alloy produce simultaneous TD and RD splittings in basal pole figures at all rolling temperatures.