Effects of different processing conditions on super-elasticity and low modulus properties of metastable β-type Ti-35Nb-2Ta-3Zr alloy

In this work, by means of X ray diffraction, polarizing microscope, transmission electron microscope and mechanical properties test, the microstructure and mechanical properties of metastable β-type Ti-35Nb-2Ta-3Zr alloy were systematically studied by two different processing techniques. The results showed that there was a large amount of lath martensite in this alloy solution-treated by 1053 K for 30 min, and recrystallization occurred, but the grain growed again and became coarse equiaxed crystal. However, the alloy annealed by 923 K for 10 min undergone recrystallization inside the grains, and many fine grains appeared. In addition, a large number of dislocations and grain boundaries that provided adequate heterogeneous nucleation conditions for β phase during annealing to promote the transformation α″ phase into β phase, so as to reduce the content of α″ phase and stabilize β phase. Therefore, the annealed specimens had lower elastic modulus (55 GPa) and higher super-elasticity (47.94%) than the solution treated specimens.