Microstructure,texture evolution and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn biomedical beta titanium alloy

Ti-32.5Nb-6.8Zr-2.7Sn (TNZS, wt%) alloy was produced by using vacuum arc melting method, followed by solution treatment and cold rolling with the area reductions of 50% and 90%. The effects of cold rolling on the microstructure, texture evolution and mechanical properties of the experimental alloy were investigated by optical microscopy, X-ray diffraction, transmission electron microscopy and universal material testing machine. The results showed that the grains of the alloy were elongated along rolling direction and stress-induced α″ martensite was not detected in the deformed samples. The plastic deformation mechanisms of the alloy were related to {112}$〈111〉$ type deformation twinning and dislocation slipping. Meanwhile, the transition from γ-fiber texture to α-fiber texture took place during cold rolling and a dominant {001}${〈110〉}_{\mathrm{\alpha }?\mathrm{f}\mathrm{i}\mathrm{b}\mathrm{e}\mathrm{r}}$ texture was obtained after 90% cold deformation. With the increase of cold deformation degree, the strength increased owing to the increase of microstrain, dislocation density and grain refinement, and the elastic modulus decreased owing to the increase of dislocation density as well as an enhanced intensity of {001}${〈110〉}_{\mathrm{\alpha }?\mathrm{f}\mathrm{i}\mathrm{b}\mathrm{e}\mathrm{r}}$ texture and a weakened intensity of {111}${〈112〉}_{\mathrm{\gamma }?\mathrm{f}\mathrm{i}\mathrm{b}\mathrm{e}\mathrm{r}}$ texture. The 90% cold rolled alloy exhibited a great potential to become a new candidate for biomedical applications, since it possesses low elastic modulus (47.1 GPa), moderate strength (883 MPa) and high elastic admissible strain (1.87%), which are superior than those of Ti-6Al-4V alloy.