Fabrication of dual-gradient microstructure and their effects on the mechanical properties of commercial pure Ti

Commercial pure Ti sheets with an initial wavy profile were rolled and annealed to fabricate heterostructure. Microstructure investigations by electron backscatter diffraction (EBSD) show that a dual-gradient microstructure including gradient grain size and gradient texture is developed, where the average grain size decreases and the split-basal texture gets stronger from the trough zone to the crest zone. Finite element simulations of the rolling process were carried out to investigate the formation mechanism of the dual-gradient microstructure. Uniaxial tension tests were performed to evaluate the mechanical properties, and the digital image correlation (DIC) technique was used to reveal the evolution of local strain during tension. When tensioned along the rolling direction, sheets consisting of both crest and trough zones achieve better elongation compared with the single crest and single trough counterparts. When tensioned along the transverse direction, better elongation is also obtained for the sheets with an initial wavy profile compared with the straight counterparts, which is mainly attributed to the dispersing local strain caused by the gradient texture. The results reported in this study may be inspirational to the design and fabrication of heterostructural hexagonal closed-packed metals.