Relationship between texture development and deformation twinning activity in Ti-15Mo alloy

Abstract

This study was performed to evaluate the effect of rolling speed on the development of texture and mechanical properties in a Ti-15(wt%)Mo alloy. Plates were initially prepared with dimensions of 100 mm (l) × 60 mm (w) × 15 mm (t) and rolled to an 88% thickness reduction. To induce the different shear strains between the surface and center of the plates, the rolling speed was varied between 3 and 56 m/min, respectively. The rolled materials were subsequently annealed at 1173 K for 60 s to obtain a recrystallized microstructure. To evaluate the mechanical properties such as yield and tensile strength as well as elongation and strain hardening, tensile tests were conducted on the rolled alloys. In addition, the texture of the rolled and annealed materials was analyzed by X-ray diffraction, and the characteristic grain boundary distribution was analyzed by electron back-scattered diffraction. It was found that different rolling speeds led to different texture development. Specifically, the γ-fiber component developed for the material rolled at low speed and contributed to the denser formation of {332}< 113 > twins, resulting in the high strain hardening exponent (n = 0.386) and uniform elongation (εu = 0.362). In contrast, the θ-fiber component developed in the material rolled at high speed and exhibited a lower density of deformation twinning, which contributed to the lower strain hardening exponent (n = 0.320) and uniform elongation (εu = 0.314) relative to the alloy rolled at low speed. Therefore, it can be concluded that enhanced twinning density depends on texture development, which is deeply related to the Schmid factor of the grains.